YALE MEDICAL LIBRARY
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B.A. Yale 1901
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THE DYNAMICS OF LIVING MATTER
ffiolumiria SEntberjsttg Biological Zziits
EDITED BY
HENRY FAIRFIELD OSBORN
AND
EDMUND B. WILSON
I. FROM THE GREEKS TO DARWIN
By Henry Fairfield Osborn
II. AMPHIOXUS AND THE ANCESTRY OF THE VERTEBRATES
By Arthur Willey
III. FISHES, LIVING AND FOSSIL. An Introductory Study
By Bashford Dean
IV. THE CELL IN DEVELOPMENT AND INHERITANCE
By Edmund B. Wilson
V. THE FOUNDATIONS OF ZOOLOGY
By W. K. Brooks
VI. THE PROTOZOA
By Gary N. Calkins
VII. REGENERATION
By T. H. Morgan
VIII. THE DYNAMICS OF LIVING MATTER
By Jacques Loeb
IX. STRUCTURE AND HABITS OF ANTS. Un preparation)
By W. M. Wheeler
X. BEHAVIOR OF THE LOWER ORGANISMS. (In preparation)
By H. S. Jennings
COLUMBIA UNIVERSITY BIOLOGICAL SERIES. VIII.
THE DYNAMICS OF LIVING
MATTER
BY
JACQUES LOEB
PROFESSOR OF PHYSIOLOGY IN THE UNIVERSITY
OF CALIFORNIA
Ke&j fgorfe
THE COLUMBIA UNIVERSITY PRESS
THE MACMILLAN COMPANY, Agents
LONDON: MACMILLAN & CO., Ltd.
1906
All rights reserved
Copyright, 1906,
By THE MACMILLAN COMPANY.
Set up and electrotyped. Published March, 1906.
■ ■ •
0 P 50?
7U3
NotfanoB yresa
J. S. Cushing- & Co. — Berwick & Smith Co.
Norwood, Mass., U.S.A.
&0
ANNE LEONARD LOEB
PREFACE
This book owes its origin to a series of eight lectures delivered
upon the invitation of Professor E. B. Wilson and Professor H. F.
Osborn at Columbia University in the spring of 1902. The aim of
the lectures was to give a presentation of my researches on the
dynamics of living matter and the views to which they had led rae.
In preparing the book I have tried to give a somewhat more com-
plete survey of the field of experimental biology than was possible
in the lectures, without, however, trying to alter their character. In
the introductory lecture use was made of my address at the Inter-
national Congress at St. Louis.
To Dr. S. S. Maxwell, who has undertaken the main burden of
reading the proof and preparing the index, and to Professor J. B.
MacCallum, who also assisted me in the reading of the proof, my
sincere thanks are due.
Berkeley, California,
January I, 1906.
CONTENTS
LECTURE I
PAGE
Introductory Remarks i
LECTURE II
Concerning the General Chemistry of Life Phenomena
1. Historical Remarks ............ 7
2. Reversible Enzyme Action — Lipase Action — Reversible Enzyme Action in the
Carbohydrate Group — The General Occurrence of Protein-splitting Enzymes 9
3. Respiration as a Catalytic Process . . . . . . . . . .13
(a) The Oxidases ............ 13
(&) Further Remarks on the Significance of Oxygen in Life Phenomena . . 16
(f) Death in Lack of Oxygen and the Protective Action of Oxygen . . 18
(d) Changes of Structure in Lack of Oxygen ... .... 19
4. The Production of CO2 through Enzymes . . . . . . . .21
5. Concerning the Theory of Enzyme Action ........ 24
(a) Stereochemical Attempts .......... 24
(3) The Theory of Intermediary Reactions ....... 26
LECTURE III
The General Physical Constitution of Living Matter
1. The Limits of Divisibility of Living Matter 29
2. Foam Structures and Emulsions .......... 31
3. The Colloidal Character of Living Matter 33
4. The Formation of Surface Films and Traube's Membranes of Precipitation —
Overton's and Meyer's Work on Narcotics and the Nature of Surface Films . 38
5. Osmotic Pressure and the Exchange of Liquids between the Cells and the Sur-
rounding Liquid ............ 41
6. Further Limitations of Traube's Theory of Semipermeability ..... 45
7. The Antagonistic Effects of Salts . . . 46
LECTURE IV
On Some Physical Manifestations of Life
1. Hypotheses of Muscular Contraction . . . . . . . . -53
2. Quincke's Theory of Protoplasmic Motion ........ 55
3. Concerning the Theory of Cell Division ......... 58
4. The Origin of Radiant Energy in Living Organisms ...... 66
5. Electrical Phenomena in Living Organisms ........ 68
CONTENTS
LECTURE V
The Role of Electrolytes in the Formation and Preservation of
Living Matter
PAGE
On the Specific Difference between the Nutritive Solutions for Plants and Animals
— Protective Solutions and Nutrient Solutions . . . . . 71
Concerning a Theory of Irritability and the Role of Na, K, and Ca for Animal Life
— Rhythmical Contractions in Skeletal Muscle, in Medusae, and the Ven-
tricle of the Heart — Contact Irritability in Muscle — Analogies to the Role
of Salts in Coagulation of Milk — Significance for the Understanding of
Functional Nervous Diseases — The Action of Purgatives .... 78
The Reaction of Living Matter and the Role of Bicarbonates in the Preservation
of Life 95
Electrical Stimulation 98
LECTURE VI
The Effects of Heat and Radiant Energy upon Living Matter
1. Effects of Heat — Upper Temperature Limit of Life — Influence of Reaction-
velocity upon Biological Processes — Lower Temperature Limit — Other
Biological Effects of Heat 106
2. General Effects of Radiant Energy upon Living Matter — Chemical Action of Light
upon Organisms 112
LECTURE VII
Heliotropism
1. The Heliotropism of Sessile Organisms . • ri7
2. Heliotropism of Free-moving Animals . . . . . . . . .124
3. The Control of the Precision and Sense of Heliotropic Reactions in Animals . . 130
4. The Reaction of Animals to Sudden Changes in the Intensity of Light . . . 135
LECTURE VIII
Further Facts concerning Tropisms and Related Phenomena
1. General Theory of Tropisms . . . . . . . . . • • 13%
2. Galvanotropism ... . . . . . . . • • • H1
3. Geotropism . . . . . . . . • • • H7
4. Chemotropism and Related Phenomena . . . . . • • • • l52
5. Stereotropism ...........■•■ J55
6. Concluding, Remarks concerning Tropismlike Reactions . . r5"
LECTURE IX
Fertilization
1. The Specific Character of the Fertilizing Power of the Spermatozoon — Hybrid
Fertilization x6l
2. Artificial Parthenogenesis and the Theory of Fertilization 164
CONTENTS xi
LECTURE X
Heredity
PAGE
1. The Hereditary Effects of the Spermatozoon and Egg — The Prevailing Influence
of the Egg in the Early Stages of Development — Merogony — Toxicity of
the Blood of Forms not closely Related — Mendel's Experiments . . .179
2. The Determination of Sex and the Secondary Sexual Characters .... 186
3. Egg Structure and Heredity ........... 191
LECTURE XI
On the Dynamics of Regenerative Processes
1. Sachs's Hypothesis of the Formation of Organs ....... 199
2. Heteromorphosis and Regeneration in Tubularia ....... 201
3. Regeneration in an Actinian ( Cerianthus membranaceus) ..... 207
4. Regeneration and Heteromorphosis in Planarians ....... 210
5. On the Influence of the Central Nervous System upon Regeneration and on Phe-
nomena of Correlation in Regeneration . ....... 213
6. The Effect of Some External Conditions upon Regeneration and the Transforma-
tion of Organs . . . . . . . . . . . .217
7. The Role of Reversible Processes in Phenomena of Regeneration — The Distribu-
tion of the Power of Regeneration in the Animal Kingdom .... 218
LECTURE XII
Concluding Remarks 223
INDEX 227
LECTURE I
INTRODUCTORY REMARKS
In these lectures we shall consider living organisms as chemical
machines, consisting essentially of colloidal material, which possess the
peculiarities of automatically developing, preserving, and reproducing
themselves. The fact that the machines which can be created by man
do not possess the power of automatic development, self-preservation,
and reproduction constitutes for the present a fundamental difference
between living machines and artificial machines. We must, however,
admit that nothing contradicts the possibility that the artificial produc-
tion of living matter may one day be accomplished. It is the purpose
of these lectures to state to what extent we are able to control the phe-
nomena of development, self-preservation, and reproduction.
Living organisms may be called chemical machines, inasmuch as
the energy for their work and functions is derived from chemical pro-
cesses, and inasmuch as the material from which the living machines
are built must be formed through chemical processes. It is therefore
only natural that the dynamics of living matter should begin with an
analysis of the specific character of the chemical processes in organisms.
It is neither our intention nor is it possible for us to give an exhaustive
analysis, and we shall only go far enough to satisfy ourselves that no
variables are found in the chemical dynamics of living matter which
cannot be found also in the chemistry of inanimate nature.
The material of which living organisms consist is essentially col-
loidal in its character. Graham introduced the discrimination between
colloidal and crystalloidal substances : the latter diffuse easily, the former
only with difficulty, or not at all, through animal membranes. The
colloidal substances may be in solution or fine suspension, or they may
appear in a jellylike or coagulated or precipitated form. In the former
case where they are liquid we speak of sols, in the latter of gels. The
structures which we find in living matter originate mostly through a
gelation or coagulation of liquid colloids. We shall see in these lectures
that liquefactions and gelations or coagulations may possibly play a
great role in various physical manifestations of life ; but as the physics
of colloids is still in its beginning, we must not be surprised that it is as
yet impossible to carry its application to life phenomena very far.
2 DYNAMICS OF LIVING MATTER
As the chemical character of life phenomena and the physical struc-
ture of living matter form the basis for the understanding of the dynamics
of living matter, it is natural that they should be the starting-point in
our lectures.
As far as the specifically biological phenomena are concerned,
namely, the phenomena of development, self-preservation, and repro-
duction, it will be our aim to analyze them as much as at present pos-
sible from a physicochemical point of view. It may perhaps be
desirable before undertaking this task fo£ us to state, as simply as
possible, some of the individual problems that will present themselves
for discussion, and the general method of their solution.
We know that the eggs of the majority of animals cannot develop
unless they are fertilized, i.e. unless they are entered by a spermato-
zoon. We do not know how the spermatozoon causes the egg to
develop, but it is not to be expected that we shall gain an insight into
these causes except by trying to imitate by purely chemical and physical
means the effects which a spermatozoon has upon the egg. We shall see
that this has been accomplished in some forms. Under ordinary condi-
tions, the egg of Strongylocenirotus purpuratus, a sea urchin of the Pacific
coast, does not develop unless a spermatozoon enters it; but the fer-
tilizing effect of a spermatozoon can be imitated in all essential details
by putting the egg for a minute into sea water to which a certain amount
of a fatty acid has been added and by subsequent exposure of the egg for
about half an hour to sea water whose concentration has been raised
by a certain amount. Similar results can be obtained in other forms.
From a given egg can arise a specific organism only, the morpho-
logical and physiological qualities of which can be predicted with cer-
tainty, if we know the organism from which the egg is derived. We
call this fact heredity. Modern embryology has shown that the com-
plicated adult forms develop gradually from simpler forms, and by
following the development from the egg we readily understand how it
happens that the adult form is so much more complicated than the egg
from which it arises. The question which has recently puzzled biolo-
gists is whether the egg has any structure which can be related to the
adult form. This seems to be true in the eggs of some forms, to the
extent at least that from the various regions of the egg somewhat differ-
ent parts of the embryo arise. We do not know the causes which deter-
mine this relatively slight differentiation inside of the egg, but we shall
see that everything indicates that these causes may be of a simple
physicochemical order. In studying the mechanism of heredity, it is
perhaps of importance to realize that as far as the heredity of the earliest
embryonic stage is concerned, it is almost, or exclusively, determined
INTRODUCTORY REMARKS 3
by the egg. This is beautifully illustrated in the case of the hybridiza-
tion of the egg of the sea urchin with the sperm of the starfish. The
development of the pure breed of the sea urchin is after a certain stage
(the gastrula stage) typically different from the development of the star-
fish, inasmuch as the sea urchin's egg forms at that point a skeleton and
goes into the characteristic pluteus form, while the starfish egg forms
no skeleton, but undergoes a different development. When the sea
urchin's egg is fertilized with starfish sperm, the egg always develops
into a pluteus, never into the corresponding starfish form. If we exam-
ine the adult forms of hybrids, however, we find that it makes no differ-
ence which of the two forms furnishes the spermatozoon or the egg.
This difference in the influence of the spermatozoon and egg upon the
early embryonic and the adult form of the offspring is possibly due to
a difference in the mass of the egg and the spermatozoon, the latter being
as a rule much smaller than the former. As soon, however, as the
embryo grows and its mass becomes large in comparison with that of
the egg, the original difference in the hereditary effects of the two sex
cells must diminish or disappear.
The foundations of a theory of heredity in the adult were laid by
Gregor Mendel in his treatise on the hybrids' of plants, and this theory
is atomistic in its character. He showed that certain simple character-
istics of plants, e.g. the round or angular form of the seeds of peas, or
the color of their endosperm, must already be represented in the germ
by definite determinants. His experiments on the hybridization of
various forms of peas indicate that each hybrid contains two kinds of
sexual cells, one possessing the determinants for the discriminating
fatherly characteristic only, the other for the discriminating motherly
characteristic. Both kinds of sexual cells seem to exist in equal numbers
in such a hybrid. A similar fact has been discovered in other cases
of hybridization, although it does not hold good for all cases. Hugo
de Vries and others have begun to build up the physiology of heredity
on the basis of Mendel's discovery.
It is obvious that no theory of evolution can be true which disagrees
with the fundamental facts of heredity. It is the merit of De Vries to
have shown that a mutation of species can be directly observed in cer-
tain groups of plants, and he has further shown that the changes occur
by jumps, not gradually. This fact harmonizes with the consequence
to be drawn from Mendel's experiments that each individual char-
acteristic of a species is represented by an individual determinant in
the germ. This determinant may be a definite chemical compound.
The transition or mutation from one form into another is therefore
only possible through the addition or disappearance of one or more
4 DYNAMICS OF LIVING MATTER
of the characteristics or determinants. If this view can be applied
generally, it is just as inconceivable that there should be gradual varia-
tions of an individual characteristic and intermediary stages between
two elementary mutations, as that there should be gradual transitions
between one alcohol and its next neighbor in a chemical series.
The fact that, as a rule, at a definite stage of development, larger
masses of sexual cells are formed, is one of the automatic phenomena
of development. The mechanism of this formation is unknown.
Miescher tried to solve this problem in the salmon. In this animal
the sexual cells seem to be formed at the expense of the substances
of the muscles, and it was the disappearance of the muscles at the time
the sexual organs began to grow which aroused Miescher' s interest.
But this seems to be after all of only secondary importance, inasmuch
as with our present knowledge of the chemistry of living organisms
it is immaterial whether the animal's own muscles furnish the material
for the sexual cells or the muscles of the animal it devours. The real
problem is, how it happens that at a certain stage in the development
of the animal the sexual glands take away so much material from the
blood. From our present knowledge we must suspect that the mechan-
ism of such a process is a transformation of liquid constituents of the
blood into solid constituents inside of those cells which show a rapid
growth or a transformation into different compounds.
We possess a little more knowledge concerning sexual dimorphism.
It has been known for a long time that it is possible to produce in plant
lice (Aphis) either females exclusively, or both sexes, at desire. In
bees and related forms, as a rule, only males originate from unfertil-
ized eggs, and females only from fertilized eggs. It is known, more-
over, that in higher vertebrates such twins as originate from the same
eggs are also uniform in sex, while twins originating from different eggs
may be different in sex. All that we know thus far concerning the
origin of sex seems to indicate that the sex of the embryo is already
determined in the unfertilized egg, or is determined very soon after the
impregnation of the egg.
Sexual maturity is sooner or later followed by death. Is death
determined just as automatically by the processes of development pre-
ceding it, e.g. the maturation of the sexual products, as are these pro-
cesses by the previous processes of development, or as is the develop-
ment of the egg by the entrance of a spermatozoon? The fact that
most higher animals, at least, die by bacterial infection, and that cer-
tain plants, e.g. the Sequoia, which are more free from bacteria, can
reach an almost fabulous age, renders the answer to this question some-
what uncertain or prevents the generalization of an answer. It is not
INTRODUCTORY REMARKS 5
impossible that further experiments on the egg may aid us in solving
this problem. In certain forms, e.g. the starfish, the mature egg, if
not fertilized, dies rapidly, while the fertilized egg continues to live.
For this egg the act of impregnation is a life-saving act.
We shall now attempt to give a short sketch of the phenomena and
problems of self-preservation similar to that just given of the phe-
nomena of development. Among the phenomena of self-preservation
are such facts as the existence of automatic mechanisms for the union
of the sexual cells wherever there exist separate sexes, or the existence
of automatic mechanisms for the deposition of eggs in places which
furnish food for the young larvae, and so on. What do we know con-
cerning the nature of these automatic mechanisms? Metaphysics
has supplied us in these cases with the terms ''instinct" and "will." We
speak of instinct when an animal, apparently unconsciously, executes
motions or actions which are necessary for the preservation of the in-
dividual or the species; while we speak of will when motions are exe-
cuted consciously. We call it instinct when the female fly deposits
her eggs on meat on which the young larvae can feed. An analysis of
the instinctive actions has yielded the result that the purposeful motions
of animals frequently depend upon mechanisms which are a function
of the symmetrical structure and the symmetrical distribution of irrita-
bility on the surface of the body of the organisms. Symmetrical points
on the surface of an animal have usually an equal irritability, i.e. if
such spots are stimulated equally the same amount of motion, but in
opposite directions, is produced. Points on the surface which are
nearer the oral pole of the animal usually have a higher irritability
than, or a different irritability from, points which are nearer the aboral
pole. If lines of force, e.g. rays of light, current curves, lines of gravi-
tation, lines of diffusion, strike one side of an animal in greater density
than the other side, the tension of the muscles, or contractile elements, on
both sides of the organism does not remain the same, and if the animal
moves, a tendency to turn to one side must result. This will continue
until symmetrical points on both sides of the animal are again struck
at the same angle by the lines of force. As soon as this occurs the ten-
sion of the muscles, or contractile elements, on both sides of the animal
becomes equal, and there is no more reason why the animal should
deviate toward the right or the left; it will therefore continue to move
in the original direction. This automatic orientation in a field of force
toward or away from the center of force is called a tropism. It has
been possible to dissolve a number of animal instincts into tropisms.
The analysis of various tropisms has shown that there exists a great
variety, and often a great complexity due to the combination of several
(5 DYNAMICS OF LIVING MATTER
forms of tropisms in the same individual, and to the changes of these
tropisms under the influence of internal and external factors. In
these lectures we shall discuss some of the elementary tropisms and
their role in the animal instincts and in the preservation of the indi-
vidual and the species.
The will actions of animals, i.e. those motions which are executed
consciously, will not be discussed here as I have already analyzed them
in another book.* I will simply state here that I consider conscious-
ness the function of a definite machine or mechanism, which we may
call the mechanism of associative memory. Whatever the nature of
this machine may be it has one essential feature in common with the
phonograph, namely, that it reproduces impressions in the same chrono-
logical order as that in which they were received. The mechanism of
associative memory seems to be. located — in vertebrates — in the cere-
bral hemispheres. It follows from the experiments of Goltz that one of
the two hemispheres is sufficient for all the phenomena of memory and
consciousness. As far as the chemical or physical mechanism of memory
is concerned, we have at present only a few vague data. H. Meyer
and Overton have pointed out that substances which are easily soluble
in fat are also, for the most part, strong anaesthetics, e.g. ether, chloro-
form, etc., and that the ganglionic cells are especially rich in lipoids.
It is possible that the mechanism of associative memory depends in
part upon the properties and activities of the fatty constituents of the
cerebral hemispheres. Another fact which may be of importance is
the observation of Speck that if the partial pressure of oxygen in the
air is lowered to below one third of its normal value, the fundament
of mental activity, namely, memory, is almost instantly interfered with,
and total loss of consciousness rapidly follows.
In those animals which possess the mechanism of associative memory,
a number of the automatically regulated processes may become con-
scious. Respiration is purely an automatic process, yet we may at any
time become conscious of it. This has misled a number of authors
to believe that such automatic processes as in ourselves may become
conscious must be accompanied by consciousness in any animal in which
they occur. These authors overlook the fact that the automatic mech-
anisms of self-preservation must occur in every organism, while an
apparatus for associative memory may be found only in a limited num-
ber of organisms. Without such an apparatus, consciousness is impos-
sible. The fact that a physiological process may become conscious
in ourselves does not therefore prove that it is accompanied by conscious-
ness in every organism.
* Loeb, Comparative Physiology of the Brain and Comparative Psychology. G. P. Put-
nam's Sons, New York.
LECTURE II
CONCERNING THE GENERAL CHEMISTRY OF LIFE PHENOMENA
i. Historical Remarks
To-day every one who is familiar with the field of chemical biology
acknowledges the fact that the chemistry of living matter is not spe-
cifically different from the chemistry of the laboratory. We owe the
certainty of this fact essentially to three publications, which may be
mentioned briefly. The first contained the proof furnished by Lavoi-
sier and La Place in 1780, that animal heat is produced by a process
of slow combustion, and that for a certain amount of heat produced
a certain amount of oxygen is consumed in the production of CO2.
A measurement of the quantity of CO2 formed and the amount of heat
produced gave approximately identical results in the case of a burning
candle and a living guinea pig.*
A second step in this direction was taken when Woehler showed
that an organic substance like urea, which is a product of metabolism,
can be made artificially in the laboratory.f To-day so many of the
compounds produced in the living body can be produced artificially
that we can hardly understand that in 1828 Woehler's discovery was
considered sensational.
The discovery of Lavoisier and La Place left a doubt in the minds
of scientists as to whether after all the dynamics of oxidations and of
chemical reactions in general is the same in living matter and in inani-
mate matter. The oxidation of food stuffs could indeed be imitated
outside the body, but only at such temperatures as were incompatible
with life; phenomena of digestion could be imitated, but only with
the aid of acids too strong for life to continue. The way out of the
difficulty was shown in a remarkable article by Berzelius. £ He pointed
out that in addition to the forces of affinity, another force is active in
* Lavoisier et De la Place, Memoire sur la Chaleiir, 1 780. CEuvres de Lavoisier, Vol. 2.
(Also in Ostwald's Klassiker der Naturwissenschaften, Nr. 40.)
t Woehler, Ueber kunstliche Bildung des Harnstoffs. Poggendorfs Annalen, Vol. 12,
p. 253, 1828.
% Berzelius, Einige Ideen uber eine bei der Bildung organischer Verbindungen in der
lebenden Natur wirksame aber bisker nicht bemerkte Kraft. Berzelius u. Woehler, Jahres-
bericht, 1836.
7
8 DYNAMICS OF LIVING MATTER
chemical reactions: this he called catalytic force. As an example
he used KirchhofFs discovery of the action of dilute acids in the hy-
drolysis of starch to dextrose. In this process the acid is not consumed,
hence Berzelius concluded that it did not act through its affinity, but
merely by its presence or its contact. Another instance quoted by
Berzelius was the decomposition of H2O2 which had been investigated
by Thenard. In acid solution this body is stable ; in alkaline solution,
or in the presence of platinum, silver, or gold, or in the presence of
fibrin of the blood, it is rapidly decomposed. In this decomposition
apparently neither the fibrin, the gold, nor the platinum acted through
the force of affinity, but catalytically. He then suggests that the spe-
cific and somewhat mysterious reactions in living organisms might be
due to such catalytic bodies as act only by their presence, without being
consumed in the process. He quotes as an example the action of
diastase in the potato. "In animals and plants there occur thousands
of catalytic processes between the tissues and the liquids." The idea
of Berzelius has proved fruitful, and the catalytic agencies which in
his opinion are responsible for the characteristic reactions in living
matter are the enzymes of modern biological chemistry. In some details,
however, Berzelius's idea was erroneous. We now know that we have
no right to assume that the catalytic bodies do not participate in the
chemical reaction because their quantity is found unaltered at the end of
the reaction. On the contrary, we shall see that it is probable that they
can exercise their influence only by participating in the reaction, and by
forming intermediary compounds, which are not stable. The catalyzers
may be unaltered at the end of the reaction, and yet participate in it.
In addition we owe to Wilhelm Ostwald* the conception that the
catalyzer does not as a rule initiate a reaction which otherwise would
not occur, but only accelerates a reaction which otherwise would indeed
occur, but too slowly to give noticeable results in a short time.
Thus the existence of catalytic agencies, the so-called enzymes in
living matter, explains the fact that chemical changes may occur very
rapidly in the body at a comparatively low temperature and at a prac-
tically neutral reaction. Catalyzers are used extensively in chemical
factories, e.g. in the manufacture of sulphuric acid, so that it is impos-
sible to see in their presence in living matter a specific difference between
the chemistry of living and inanimate nature. The only difference
is, perhaps, that living matter manufactures its own catalyzers. This,
however, is part of that peculiarity mentioned in the introductory lec-
ture, that living machines possess the peculiarity of automatically pre-
serving themselves.
* W. Ostwald, Lehrbuch der allgemeinen Chemie, Vol. II, 2d part, p. 248, 1902.
GENERAL CHEMISTRY OF LIFE PHENOMENA
2. Reversible Enzyme Actions
Reversible chemical processes are characterized by the fact that
the reaction comes to a standstill before all the substances on one side
of the equation are transformed into those on the other side. The
reason is, that a point is reached when, in the unit of time, the change
in one direction is just as great as the change in the opposite direction.
When this occurs we say that chemical equilibrium has been established.
Inasmuch as, according to Ostwald, enzymes do not inaugurate chem-
ical reactions, but only accelerate them, it follows that the action of
enzymes must also be reversible, if the process itself is reversible. It
is the merit of Arthur Croft Hill to have first shown a few years ago
that an enzyme, maltase, which accelerates the hydrolysis of maltose
into dextrose, also accelerates the synthesis of dextrose into maltose
when added to pure dextrose. It is no exaggeration to say that Hill's
paper entirely changed the conceptions of the physiology of metabolism.
We shall return to Hill's experiments later, and first discuss the revers-
ible action of a fat-splitting enzyme, lipase.
It had been known for some time that the pancreas secretes an
enzyme which digests fat in the intestinal canal. Kastle and Loeven-
hart* showed that in all tissues and liquids of the body which contain
fat, lipase can be found. A watery extract of pancreas contains a sub-
stance in solution which is capable of hydrolizing fats, i.e. of splitting
fats into fatty acid and alcohol. Kastle and Loevenhart showed, more-
over, that the watery extract of any tissue which contains fat acts in a
similar way. The chemical character of this catalytic substance is
unknown, except that its efficiency is rapidly destroyed if it is heated
in water. According to Taylor, \ it does itself, at a high temperature,
undergo a hydrolytic cleavage.
Kastle and Loevenhart showed that lipase not only accelerates the
hydrolysis of fat, but also the synthesis of fat, when added to a mixture
of fatty acid and alcohol. Their experiments were made on ethylbuty-
rate. If an extract from the pancreas or fiver was added to a mixture
of ethylalcohol and butyric acid, ethylbutyrate was formed. This
reversible action of lipase has the effect that the process of digestion of
fat can only be completed if the products of digestion are removed.
In the intestine this occurs through absorption.
The velocity of the hydrolysis of ethylbutyrate was found to be in
proportion to the concentration of the lipase. This explains the fact
* Kastle and Loevenhart, Am. Chem. Journal, Vol. 24, p. 491, 1900.
t A. E. Taylor, University of California Publications, Pathology, Vol. I, p. 33, 1904.
10 DYNAMICS OF LIVING MATTER
that those tissues which possess most fat, as a rule, also possess most
lipase.* The more lipase a cell possesses the quicker it will be able
to convert the fatty acid and alcohol, which diffuse or are absorbed
into it from the blood, into fat ; and hence more fatty acid and alcohol
must diffuse into such a cell in the same length of time from the blood
than into a cell with less lipase.
We understand how it happens that in times of abundant fat supply
our tissues are able to store up fat, while in times of want fat disappears
from them. If the blood receives no fat from the intestine, and if the
other sources of fat formation, which we shall mention later, cease,
the digestive effect of the lipase in the cells must outweigh its synthet-
ical action.
The experiments of Kastle and Loevenhart were not tried with the
fats occurring in the body. A. E. Taylor f has filled this gap by showing
that the lipase extracted from the castor bean, which digests fats, is
able to produce synthetically the triglyceride of oleic acid. The pro-
cess is a very slow one, inasmuch as in six months only 3.5 g. of the
fat were formed. Taylor concludes that in the body other agencies
than mere enzymes must contribute toward the acceleration of the
hydrolytic, as well as the synthetical processes. These conditions
are, however, not of a vitalistic character, but may be due to the pres-
ence of certain other substances. Thus Hewlett has recently found in
Taylor's laboratory that the addition of lecithin to lipase accelerates
the hydrolysis of fat considerably. Taylor found also that the lipase
from the castor bean cannot synthetize every fat, but only the triglycer-
ide of oleic acid. Experiments with palmitic and stearic acid and
glycerine as an alcohol gave negative results, as gave also experiments
with oleic acid and mannit or dulcit as alcohol. This is in harmony
with the theory of intermediary reactions, which will be discussed
later.
It is, however, worth mentioning that fat may be produced in the
body from carbohydrates, and that lipase has, as far as we can tell,
nothing to do with this mode of fat formation. The most striking case
of such an origin of fat is found in the leaves of the olive tree, which
synthetize it from the carbohydrates formed from the C02 of the air.
The fact that a reduction must form part of the process of the forma-
tion of fat from carbohydrates may explain why so often a hypertrophic
heart has a tendency to fatty degeneration, inasmuch as the hyper-
trophic heart is as a rule an overworking heart, and is thus liable to
suffer from lack of oxygen.
* Loevenhart, Am. Jour. Physiology, Vol. 6, p. 331, 1902.
t A. E. Taylor, University of California Publications, Pathology, Vol. I, p. 33, 1904.
GENERAL CHEMISTRY OF LIFE PHENOMENA
II
Neilson* has shown that the catalytic action of lipase on ethylbuty-
rate can be imitated by platinum-black. The latter not only acceler-
ates the hydrolysis, but also the synthesis of ethylbutyrate. Kastle
and Loevenhart found that certain poisons like hydrocyanic or sali-
cylic acid weaken the action of lipase. Neilson found that these poisons
act similarly on the digestion of ethylbutyrate by platinum-black.
The study of the reversible action of enzymes in the carbohydrate
group is complicated by the fact that the digestion of starch to sugar
occurs in a series of successive stages, and that apparently each stage
requires a different catalyzer. According to Duclaux,f we possess
specific enzymes for the transformation of solid into liquid starch; the
liquid starch is then split by amylase or diastase into a disaccharide,
i.e. maltose. Maltose is split by the enzyme maltase into ^-glucose.
In case another disaccharide is formed in the place of maltose, other
enzymes are required, e.g. in the case of cane sugar, invertase, whereby
dextrose and laevulose are formed. In the animal body, glycogen is
formed in the place of starch. It is obvious that the synthesis of dex-
trose into glycogen or starch requires the presence of several catalyzers.
The action of these catalyzers must be studied individually.
Hill^ found that the hydrolysis of maltose in the presence of the
enzyme maltase is retarded if dextrose is added to the maltose; that,
moreover, the hydrolysis of maltose under the influence of maltase is
complete only in very dilute solutions, while the reaction otherwise
comes to a standstill before all the maltose is transformed into glucose.
The following table shows the point at which the hydrolysis comes to
a standstill at various concentrations: —
Concentration of Maltose
40%
IO%
4%
2%
Percentage of Maltose which
is split into Glucose
84%
94-5 %
98%
99%
Hill convinced himself that if the enzyme maltase is added to a solu-
tion of glucose, maltose is formed, and that, moreover, equilibrium
is reached at the same point as in the case of hydrolysis. When he
added fresh maltase to a 40 per cent solution of dextrose in one
experiment, 14.5 per cent, and in another 15.5 per cent, maltose
was formed. It has since been shown that the synthetical product
formed in this case was isomaltose instead of maltose, but this slight
deviation does not alter the principal result.
* Neilson, Am. Jour. Physiology, Vol. 10, p. 191, 1903.
• f Duclaux, Traite de microbiologie, Vol. 2, Paris, 1899.
% A. C. Hill, Jour. Chevi. Society, Vol. 73, p. 634, 1898.
12 DYNAMICS OF LIVING MATTER
Hill raises the question, as to whether or not a synthetical forma-
tion of maltose under the influence of maltase may occur in the living
cell. He points out that for such a result a high concentration of
dextrose in the blood is by no means necessary; that it is sufficient
if the product of the synthesis is removed immediately, possibly
through a further synthesis into' a higher carbohydrate by another
enzyme in the cell. In this way the concentration of the maltose is
kept at zero, and the tendency toward the establishment of the chemical
equilibrium must favor the further synthesis.
The synthesis of sugar into glycogen is of general importance, inas-
much as glycogen is the form in which the carbohydrates are stored
in our liver and muscles. Max Cremer* immediately after the appear-
ance of Hill's paper published the important observation, that the juice
pressed out from yeast, which had previously been rendered free from
glycogen, is capable of forming glycogen from sugar. When 10 per
cent of a fermentable sugar was added to the juice, the latter gave the
glycogen reaction after from twelve to twenty-four hours, but this
result was not obtained in all cases.
It may perhaps not be unnecessary to call attention to the fact that
in all the cases we have discussed the enzymes are soluble substances,
which can be extracted from the cells, and therefore can exist inde-
pendently of the life or structure of the cell from which they are
obtained.
In the group of proteins we not only meet with the same difficulties
which are found in the group of carbohydrates, but also with the addi-
tional difficulty, that we know considerably less about the constitution
and configuration of the various protein molecules than of the carbo-
hydrates. These two conditions probably account for the fact that
a direct reversion of the action of a hydrolytic enzyme has not yet been
satisfactorily proven for proteins.
It is hardly necessary to mention especially the fact that hydro-
lytic enzymes, e.g. of the type of trypsin, acting on proteins, are found
not only in the intestine, but also in tissues, probably generally. Thus
Salkowski has shown that if yeast cells or muscles are kept aseptically
in an incubator, an autodigestion occurs in which leucin and tyrosin,
i.e. typical end products of proteolysis, are formed.
Kutscher f has completed the proof by showing that, in addition
to the acids, the other end products of proteolysis are formed in the
autodigestion of yeast; namely, the hexonbases, e.g. arginin and lysin.
He found, moreover, that in starving yeast the above-mentioned end
* Cremer, Ber. der dcut. chem. GeselL, Vol. 32, p. 2062, 1899.
f Kutscher, Hoppe-Seyler' s Zeitsch. fur physiolog. Chemie, Vol. 32, p. 59, 1901.
GENERAL CHEMISTRY OF LIFE PHENOMENA 13
products of tryptic hydrolysis are found in considerable quantities,
while these products could be obtained in fresh and well-nourished
yeast only in minimal quantities. In this he sees, and probably cor-
rectly, an indication of the reversible action of the proteolytic enzymes.
There is, however, one essential link missing, i.e. the proof that the
hydrolytic action of the proteolytic enzymes is retarded, and finally
inhibited, when the products of digestion are not removed.
R. O. Herzog has recently made an attempt to prove the reversible
action of enzymes in a very interesting way upon the discussion of
which, however, we cannot enter here.
3. Respiration as a Catalytic Process. Oxidation and Oxidases
By respiration we mean the taking up of oxygen and the giving off
of C02. We shall see later that the latter process can exist indepen-
dently of the taking up of oxygen.
Since the days of Lavoisier and La Place the real problem of oxida-
tion has consisted in the explanation of the fact that at the body tem-
perature our food stuffs are not oxidized at all, or only infinitely slowly,
outside the body, while in the body they are oxidized rapidly. The
solution of the problem was found in the discovery of "oxidizing fer-
ments" in living organisms. This conception is chiefly due to Moritz
Traube,* who was also the first to recognize that the oxidations occur
in the cells, and not, as had been assumed before, in the lungs or the
blood.
Traube' s idea was that there exist in the cells autoxidizable sub-
stances, i.e. substances which bind loosely the free oxygen at a com-
paratively low temperature, and which are capable of giving off their
oxygen to disoxidizable substances, such as our food stuffs. It is obvious
that Traube's idea of the action of an oxidizing ferment was that of
intermediary reactions. He realized also that these oxidizing ferments
exhibited no effects which could not be produced in inanimate nature,
as the following quotation shows: "The ability to transfer oxygen . . .
is found in many, even inorganic bodies. There are substances like
nitrogenoxide, platinum, various coloring matters, copper salts, which
are capable of transferring free oxygen upon neighboring substances." f
* M. Traube, Ueber die Beziehung der Respiration zur Muskelthatigkeit und die Bedeu-
tung der Respiration uberhaupt, 1861. Gesammelte Abhandlungen von M. Traube,-^. 157,
Berlin, 1899. (In this paper Traube showed also that the work of the muscle is normally
done at the expense of carbohydrates. His arguments induced Fick and Wislicenus to try
the classical experiment by which this theory was proved.)
t M. Traube, Die Chemische Theorie der Ferment wirkungen und der Chetnismus der Res-
piration, 1878. Gesammelte Abhandl., p. 384, Berlin, 1898.
14 DYNAMICS OF LIVING MATTER
I think Jacquet* was the first to separate a "ferment of oxidation "
from the living organism, and to obtain it in a watery extract from
tissues. The oxygen of the air oxidizes benzylalcohol (C6HSCH OH)
only slowly to benzoic acid (C6H5COOH) at body temperature; the
OH
same is true for the oxidation of salicylaldehyde C6H4r,n-H-to salicylic
OH ^U-tl
acid C6H4r,nn-H-« Schmiedeberg had already shown that the animal
tissues accomplish this oxidation comparatively rapidly. Jacquet
proved that this energetic oxidation of benzylalcohol is not dependent
upon living protoplasm, as he found that it occurred also in dead tissues.
Tissues poisoned with carbolic acid continue to accelerate these oxida
tions, and even tissues which have been preserved in alcohol are capable
of so doing. Nor are these oxidations dependent upon the structure
of the cells, as watery extract from the cells also had oxidative effects
upon benzylalcohol. The action of the oxidizing enzymes is annihi-
lated when they are heated to a temperature of about ioo° — pos-
sibly through a hydrolysis of the enzyme itself.
Engler and Wild f have found that there exists a group of substances
which behave like Traube's autoxidizable substances. These sub-
stances have the peculiarity of easily forming peroxides of the following
type: —
R-O °r <<l
These peroxides are capable of giving off one atom of oxygen to dis-
oxidizable substances. Through the loss of this atom of oxygen the
peroxides are transformed into oxides. This view is supported by an
important observation which was first made by van't Hoff and Jorissen.
If the quantity of oxygen which disappears in the oxidation of a known
quantity of a disoxidizable substance is measured, it is found to be in
most cases exactly twice as large as the quantity required for the oxida-
tion of the disoxidizable substance. % This finds its explanation in the
fact that for every molecule of oxygen which is taken up by the autoxi-
dizable substance, only one atom is transferred to the disoxidizable
substance.
The view of Engler and Wild is also supported by the investigations
of Kastle and Loevenhart § on the oxidizing effects of plant tissues,
e.g. the potato, and their watery extracts. They found that organic
* Jacquet, Arch, fur experimentelle Pathologie und Pharmakologie, Vol. 29, p. 386, 1892.
t Engler und Wild, Ber. der deutsch. chem. Gesellsch., Vol. 30, p. 1669, 1897. Engler und
Weissberg, Kritische Studien iiber die Vorg'dnge der Autoxydation, Braunschweig, 1904.
\ See also Manchot, Zeitsch. filr anorganische Chemie, Vol. 27, p. 420, 1901.
§ Kastle and Loevenhart, Am. Chem. fourna/, Vol. 26, 1901.
GENERAL CHEMISTRY OF LIFE PHENOMENA 15
peroxides, e.g. benzoylperoxide, phthalylperoxide, and succinylperox-
ide, or inorganic ones, like lead peroxide and manganese peroxide, pro-
duced the same blue color in the tincture of guaiacum as the tissues
of plants, or watery extracts from the same. The production of this
blue color is due to oxidation. The same authors showed, moreover,
that the same poisons which in plants prevent the action of oxi-
dases — this is the name given to the enzymes of oxidation — prevent
also the oxidizing action of the above-mentioned organic and inorganic
peroxides upon tincture of guaiacum. Kastle and Loevenhart there-
fore conclude that the oxidases, or oxidizing enzymes, in the tissues of
animals and plants, are organic peroxides.
Here we meet with a difficulty, however. Oxidations occur inces-
santly on a large scale in the living body, especially at the temperature
of the warm-blooded animals. The peroxides, however, are not capable
of transferring oxygen in unlimited quantities to disoxidizable sub-
stances, but as soon as a peroxide molecule has given off one atom of
oxygen, its oxidizing power is at an end. This difficulty can be over-
come in the following two ways: it is possible that new autoxidizable
substances are formed incessantly in the body; the second possibility
is the existence of a second class of oxidizing enzymes which act more
in the sense of true enzymes than the peroxides, inasmuch as they are
able to take up and give off oxygen indefinitely. Haemoglobin is
capable of binding and setting free oxygen indefinitely, but it is not
capable of transferring its oxygen to disoxidizable substances, and
hence does not act as an oxidase.
The question of localization of the oxidizing enzyme in the cell was
raised by Spitzer.* He found that the proteins which can be extracted
from the cells do not possess the qualities of Jacquet's oxidase, but that
these qualities are found in such extracts as contain nucleoproteids.
The nucleoproteids are typical constituents of the cell nucleus, and
they differ from the proteins proper in that they contain P04 and Fe.
Spitzer was able to show, moreover, that of the products of cleavage
of nucleoproteids only those constituents were able to act as oxidases
which contained the Fe group. Two years ago I pointed out that if
Spitzer's researches are correct, the cell nucleus must be regarded as
the essential respiratory or oxidizing organ of the cell.f
It is possible that we have two groups of oxidizing catalyzers in the
tissues : first, those of the type of peroxides which are possibly present
in the protoplasm; and second, substances which can act indefinitely
as oxidases, and are found in the nucleus. There are, indeed, a number
* Spitzer, Pfluger's Archiv, Vol. 67, p. 615, 1897.
t Loeb, Zeitsch. fur Entwickelungsmeckanik, Vol. 8, p. 689, 1899.
16 DYNAMICS OF LIVING MATTER
of facts which seem to harmonize with the idea that the nucleus is the
main oxidizing organ of the cell. .Processes of regeneration demand
oxygen. Nussbaum* has shown that if an Infusorian be cut in such
a way as to divide it into two pieces, one containing the nucleus, and
one without any nuclear matter, only the former is capable of regenerat-
ing the lost parts. The other piece lives but a comparatively short
time and is not capable of regeneration ; it dies under symptoms which
are rather similar to death from lack of oxygen.
Ralph Lillie f tried to test the idea that the nucleus is the main oxi-
dizing organ with the aid of staining substances which diffuse into the
cell, and change color when they are oxidized. He worked with the
cells of the blood, the liver, and the kidneys of frogs, and found that
the oxidation seems to occur most rapidly in the nucleus and on its
surface. He found, moreover, that the oxidations were most rapid
in those organs and those regions of organs where the nuclei were
densest.
It has been noticed that if cells containing chlorophyll are deprived
of their nucleus, they keep alive longer if exposed to the light than if
kept in the dark. This may be connected with the fact that in the
light the chlorophyll is capable of liberating the oxygen from the C02.
It is stated, as a rule, that the role of the oxygen is to supply the
energy for the production of heat and of mechanical work, but it is
evident that this statement does not take into consideration the fact
that sessile plants, in which the loss of heat does not need to be com-
pensated by a production of heat, and in which no energy is spent in
mechanical motion, are in need of oxygen and possess oxidases. With
the exception of a limited number of anaerobic bacteria, the statement
can be made that oxidations and the presence of oxidases is a general
characteristic of living matter. There are, however, other vital processes
which are more general than those of locomotion and heat production,
which also require oxygen, i.e. cell division and growth. Pasteur made
the fundamental discovery % that with lack of oxygen the yeast cells
continue to produce lively fermentations of sugar, — in fact, Pasteur
stated that their fermentative action is more energetic than in the
presence of oxygen, — but that they grow and multiply very little or
not at all. If, however, oxygen is added freely, the yeast cells multiply
and grow considerably, provided the necessary nutritive salts are
present. According to Hoppe-Seyler and Duclaux, the absence of
oxygen favors the formation of the catalyzer for the alcoholic fermenta-
* M. Nussbaum, Arch, fur mikroscop. Anatomie, Vol. 26, 1886.
f Ralph Lillie, Am. Jour. Physiology, Vol. 7, p. 412, 1902.
% Pasteur, Etudes sur la biere, Paris, 1876.
GENERAL CHEMISTRY OF LIFE PHENOMENA 17
tion in the yeast cell, the zymase ; * but we are here chiefly concerned
with the fact which nobody has failed to confirm, that the presence of
oxygen favors cell division and growth in yeast cells; that without
oxygen these processes soon come to a standstill. The same is true
for animals. I made a large number of experiments on the effects of
lack of oxygen on the newly fertilized eggs of sea urchins and fishes
(Fundulus and Ctenolabrus).| The eggs were kept in small Engel-
mann gas chambers through which a current of hydrogen was sent to
drive out the oxygen and the C02 formed by the eggs. In the eggs of
sea urchins and Ctenolabrus, the segmentation stopped in less than an
hour after the beginning of the current of hydrogen. When the air was
again admitted, the eggs began to divide, provided they had not remained
too long without oxygen. The eggs of Fundulus, also a marine fish,
do not respond as quickly, inasmuch as it required about twelve hours
before they stopped segmenting in the current of hydrogen. Similar
results were obtained by Godlewski % on the eggs of frogs. As far as
growth and regeneration are concerned, I have found that without
oxygen both are impossible in Hydroids (Tubularia).§ In plants,
conditions are the same; seeds require a comparatively abundant
supply of oxygen for germination. || The question arises, as to what
connection exists between the oxidations in living tissues, and cell divi-
sion and growth. We cannot answer this question as we do not know
into which form of energy chemical energy must be transformed in
order to produce cell division and growth. But another point may
be settled. For the process of growth an increase in the quantity of
living matter is required, and this requires synthetical processes.
Schmiedeberg has called attention to the fact that oxygen is especially
fitted to serve as a connecting link between organic radicals, and that
through the intervention of oxygen a great many syntheses in the
body may occur. He mentions, as an example, the combination in
which sulphuric acid may appear in the urine. When a dog is fed with
benzol, the benzol appears in the urine as benzolsulphate, provided
that enough free oxygen is present. According to Schmiedeberg,
this synthesis occurs in the following way : —
2 S°2OH + 2 CfiH6 + °2 = 2 S°2_ O— C H + 2 H °*
* H. Buchner denies that lack of oxygen increases the rate of alcoholic fermentation by
yeast, although the facts seem to speak in favor of Pasteur's statement. E. Buchner, H.
Buchner, und M. Hahn, Die Zymasegarung, Miinchen und Berlin, 1903.
t Loeb, Pfliiger's Archiv, Vol. 62, p. 249, 1895.
J Godlewski, Zeits.filr Entwickelwigsmechanik, Vol. II, p. 585, 1901.
§ Loeb, Untersuchungen zur physiologischen Morphologie der Tiere, II, Wiirzburg, 1891.
|| M. Traube, Gesammelte Abhandlungen, p. 148.
c
1 8 DYNAMICS OF LIVING MATTER
It is quite possible that the idea of Schmiedeberg will prove ex-
tremely fertile in further work in this direction.*
But even this addition does not exhaust the role of oxygen in life
phenomena; there are indications which make it appear as though
the oxygen acted as a protective substance. When respiration is
interrupted for but a short time in mammals or birds, loss of conscious-
ness, and very soon death, follow. Lack of oxygen therefore affects
first the cerebral hemispheres, and especially the ganglion cells. The
blood supply to the nerves is either lacking, or is so meager that we
must conclude that the functions of the nerves require very little oxygen.
The experience in drowning shows that lack of oxygen leads in a limited
number of minutes to death. In the case of death through lack of
oxygen, the respiratory ganglia evidently undergo irreversible changes,
which make attempts at revival futile. The heart retains its irritability
much longer than the respiratory ganglia. Kuliabko has recently
shown that the heart of a child can be caused to beat, or to show fibrillary
contractions, eighteen hours after death. f This shows that death was
not due to the inability of the heart to resume its beat, but to the inability
of the respiratory ganglia to work properly. It has often been observed
in my laboratory that in dying larvae of fish or frogs the respiration
stopped sooner than the heartbeat. The irreversible changes which
mark death occur with unequal rapidity in the various tissues of an
animal.
When the egg of a Fundulus is kept in an atmosphere of pure hydro-
gen, segmentation comes to a standstill in about twelve hours, but
permanent death occurs much later. The time required for permanent
death to occur in the absence of oxygen is the longer the younger the
egg. When eggs were deprived of oxygen immediately after fertiliza-
tion, they remained alive in the absence of oxygen for three or four
days (at a temperature of about 2 2°). When embryos of three days
were exposed to the same condition, death occurred in about thirty-
four hours.
The higher the temperature the sooner lack of oxygen seems to cause
death. I make this statement on the basis of casual observations, and
I do not know whether or not any definite experiments exist on this
point; should further investigation confirm this idea, it would seem to
indicate that the changes in the tissues which cause death are produced
by noxious substances formed in the absence of oxygen. Araki J found
that in the active muscle dextrose and lactic acid are found when the
* O. Schmiedeberg, Archiv fur experiment. Pathologie und Pharmakologie, Vol. 14,
pp. 288 and 379, 1 881.
t Kuliabko, P/Tuger's Archiv, Vol. 97, p. 539, 1903.
% Araki, Zeitsck. fur physiol. Chemie, Vol. 15, p. 335, 1891.
GENERAL CHEMISTRY OF LIFE PHENOMENA 19
muscle works in lack of oxygen, while these substances are not found
in the presence of abundant oxygen. They are probably formed in
the latter case also ; but if atmospheric oxygen is present, are immediately
oxidized, while in the case of lack of oxygen they remain in the muscle.
This may serve as an example of the fact that metabolism in the presence
of abundant oxygen is different from that in lack of oxygen. Richet
and Broca have shown that if an excised muscle is stimulated in the
presence of oxygen until fatigue sets in, it will recover, but not if stimu-
lated in the absence of oxygen. It stands to reason that in the latter
case the recovery is prevented by noxious substances which would
have been oxidized and rendered harmless in the presence of oxygen.
Bacteriology furnishes examples of the fact that in the case of lack
of oxygen more virulent substances may be formed, or exist, than in
the presence of atmospheric oxygen. Kastle quotes the statement that
the toxin of the diphtheria bacillus is weakened under the influence of
light in the presence of free oxygen, while the light has no such effect
in the absence of oxygen. Pasteur observed that cultures of the anthrax
bacillus and of chicken cholera become less poisonous when exposed
to the air. Recent experiments by Kastle and Elvove* have shown
that substances which have a high reducing power are especially toxic,
and these authors are inclined to assume that many toxins belong to
the group of reducing poisons.
The fact that lack of oxygen is capable of producing irreversible
changes, and thus death, is rendered more easily comprehensible through
the direct observation of physical changes of living matter under such
conditions. I have made such observations in the segmenting egg of
a teleost fish, Ctenolabrus.f When these eggs are deprived of oxygen
at the time they reach the 8 or 16 cell stage, it can be noticed that the
membranes of the blastomeres are transformed into small droplets
within half an hour or more, according to the temperature. These
droplets begin to flow together, forming larger drops. Figures 1 to 5
show the successive stages of this process. When the eggs are exposed
to the air in time, segmentation can begin again ; but if a slightly longer
time is allowed to elapse, the process becomes irreversible and life becomes
extinct. Such clear structural changes cannot be observed in the eggs
of other animals under the same conditions. Are these changes of
structure (apparently liquefactions of solid elements) responsible for
death under such conditions? In order to obtain an answer to this
question, I investigated the effect of the lack of oxygen upon the heart-
beat of the embryo of Ctenolabrus. The egg of this fish is perfectly trans-
* Kastle and Elvove, Am. Chem. Journal, Vol. 31, p. 195, 1904.
t Loeb, Pft'ugefs Archiv, Vol. 62, p. 249, 1895.
20 DYNAMICS OF LIVING MATTER
parent and the heartbeat can easily be watched. When such eggs are
put into an Engelmann gas chamber and a current of pure hydrogen
is sent through, the heart may cease to beat in fifteen or twenty minutes;
the heart stops beating suddenly before the number of heartbeats has
diminished noticeably: it ceases beating before all the free oxygen
may have had time to diffuse from the egg. In one case the heart beat
ninety times per minute before the hydrogen was sent through; four
minutes after the current of hydrogen had passed through the gas
chamber, the rate of the heartbeat was eighty- seven per minute, three
Fig. i.
Fig. 2.
^^fxf^i cs^cskJf...
Fig. 4. Fig. 5.
Fig. 3.
FIGS. 1-5. Liquefaction of the cell walls of the egg of Ctenolabrus due to lack of oxygen.
(From Nature.) The eggs were exposed to a current of hydrogen. The liquefaction of the cell
walls and the formation of droplets began when the egg was in the 8 cell stage (Fig. 2).
These droplets fuse into larger drops and finally nothing but these drops indicates the existence
of the germinal disk. Figures 2, 3, and 4, are drawn in intervals of 15 minutes.
minutes later it was seventy-seven, and then the heart suddenly stopped
beating. It is hard to believe that this standstill could have been
caused by lack of energy. Hydrolytic processes alone could furnish
sufficient energy to maintain the heartbeat for some time, even if all
the oxygen had been used up. The suddenness of the standstill at the
time when the rate had hardly diminished seems to correspond much
more to a sudden collapse of the machine ; it might be that liquefactions
or some other change of structure occurs in the heart or its ganglion
cells, comparable to that which we mentioned before. In another
fish, Fundulus, where the cleavage cells undergo no visible changes in
the case of lack of oxygen, the heart of the embryo can continue to
beat for about twelve hours in a current of hydrogen. In this case the
rate of the heartbeat sinks during the first hour in the hydrogen current
GENERAL CHEMISTRY OF LIFE PHENOMENA 21
from about one hundred to twenty or ten per minute : then it continues
to beat at this rate for ten hours or more. In this case one might
believe that during the period of steady diminution of the tension of
oxygen in the heart (during the first hour), the heartbeat sinks steadily,
while it keeps up at a low but steady rate as long as the energy for the
beat is supplied solely by hydrolytic processes ; but there is certainly no
change in the physical structure of the cells noticeable in Fundulus,
and consequently there is no sudden standstill of the heart.
Budgett has observed that in many Infusorians visible changes of
structure occur in the case of lack of oxygen ; * as a rule the membrane
of the Infusorian bursts or breaks at one point, whereby the liquid
contents flow out. Hardesty and I found that Paramcecium becomes
more strongly vacuolized when deprived of oxygen, and at last bursts.
Amoebae likewise become vacuolized and burst under these conditions.
Budgett found that a number of poisons, such as potassium cyanide,
morphine, quinine, antipyrine, nicotine, and atropine, produce struc-
tural changes of the same character as those described for lack of oxygen.
As far as KCN is concerned, Schoenbein had already observed that it
retards the oxidation in the tissues, and Claude Bernard and Geppert
confirmed this observation. For the alkaloids, W. S. Young has shown
that they are capable of retarding certain processes of autoxidation.
This accounts for the fact that the above-mentioned poisons produce
changes similar to those observed in the case of lack of oxygen.
4. The Production of C02 through Enzymes
It seems that organisms are pretty generally capable of producing
C02 from certain organic compounds, without the presence of free
oxygen. The classical case of the production of C02 through a process
of cleavage is the alcoholic fermentation of sugar under the influence
of yeast cells. In this case one molecule of dextrose is split into two
molecules of C02 and two of ethylalcohol. The process occurs in the
absence of oxygen as well as in its presence, or, according to Pasteur,
even better in the absence of oxygen than in its presence. The catalyzer
in this case is an enzyme, the zymase, which Buchner succeeded in
liberating from the yeast cell. This discovery is of special interest,
as for years it was impossible to separate this enzyme from the cell.
Pasteur even went so far as to maintain that the process of alcoholic
fermentation was of an altogether different kind from that of the inver-
sion of cane sugar, as the latter was due to an enzyme, soluble in water,
which could easily be extracted from the cell; while this was not so in
* Budgett, Am. Jour. Physiology, Vol. 1, p. 210, 1898.
22 DYNAMICS OF LIVING MATTER
the case of the alcoholic fermentation. Buchner * showed that Pasteur f
was mistaken, and that the only difference was a technical one, inasmuch
as it requires a greater pressure to force the zymase out of the yeast
cell than other enzymes, e.g. invertase. Through the discovery of
Buchner, Biology was relieved of another fragment of mysticism. The
splitting up of sugar into C02 and alcohol is no more the effect of a
"vital principle" than the splitting up of cane sugar by invertase. The
history of this problem is instructive, as it warns us against considering
problems as beyond our reach because they have not yet found their
solution. The enzyme for the alcoholic fermentation of sugar is not
confined to yeast, but seems to occur more generally. Thus Pasteur
had already mentioned that certain kinds of fruit in the absence of air
produced alcohol besides C02 ; it is possible, however, that in fruits
alcohol forms only an intermediary product which is oxidized further,
or undergoes further changes, in the presence of oxygen, while it remains
unaltered in the absence of oxygen. Godlewski and Polzeniusz demon-
strated an alcoholic fermentation in seeds of plants which germinated
in the absence of oxygen. J The fact that in these cases the alcoholic
fermentation occurs only in the absence of oxygen seems to favor Pas-
teur's statement, that lack of oxygen increases the velocity of the fermen-
tative action of yeast in the case of alcoholic fermentation.
Stoklasa § and his pupils showed that in a number of plants and
germinating seeds C02 and alcohol are formed in the absence of oxygen
in the same proportion in which these substances appear in the alcoholic
fermentation of sugar, and that just ,as much dry substance from the
plants disappeared as corresponded to the sugar that was fermented.
They succeeded in extracting from these plants (roots of sugar beets,
potatoes, seeds of peas, seedlings of barley) an enzyme which acted
like Buchner's zymase.
As far as animals are concerned, G. von Liebig had already shown
that the muscles continue to produce C02 in the absence of air, and
that the production of C02 is increased when the muscle becomes
active. Hermann repeated these experiments, and made sure that the
muscle continues to produce C02, even if it does not contain any free
oxygen which can be extracted in the vacuum. Inasmuch as glycogen
disappears during activity, it looks as if the C02 formed in the absence
* E. Buchner, H. Buchner, und M. Hahn, Die Zymasewirkung, MQnchen und Berlin,
1903.
t Pasteur, Etudes sur la Here, Paris, 1876. Annates de chimie et de physique, Vol. 58,
p. 323, i860. See also Liebig, Ueber Gahrung, uber Quelle der Muskelkraft und Ern'dh-
rung, Leipzig und Heidelberg, 1870.
% Godlewski et Polzeniusz, Bulletin de PAcad. de Cracovie, 1901.
§ Stoklasa, Hofmei'ster 's Beitrage zur chemischen Physiologie, Vol. 3, p. 460, 1902.
Pfliiger's Archiv, Vol. 101, p. 311, 1904.
GENERAL CHEMISTRY OF LIFE PHENOMENA 23
of oxygen were produced from glycogen or sugar. If this be correct,
a process must, under such conditions, occur which bears a certain
resemblance to the alcoholic fermentation of sugar, although in the
place of alcohol another product may be formed.
It was remarkable that in spite of these observations and the well-
known fact that the muscles are the main seat for the production of
C02, nobody was able to show that a muscle extract is able to decompose
dextrose. This gap seems to have been filled recently by Cohnheim.*
Von Mering and Minkowski had found that extirpation of the pancreas
causes the most serious type of diabetes. This fact and subsequent
discoveries suggested that the pancreas must secrete a substance into
the blood, by which the oxidation or cleavage of sugar is accelerated.
The place of the decomposition of the sugar must evidently be the
muscles. Starting from these arguments, Cohnheim tested whether
the muscle and the pancreas together do not contain a glycolytic power
which neither contains alone. Cohnheim succeeded in showing that,
by a process similar to that used by Buchner, liquids free from cells
can be extracted from muscles and pancreas which, if mixed, cause
dextrose, when added to the mixture, to disappear from it. The liquid
extract from the muscle or the pancreas alone has no such action. "This
observation may be analogous to the discovery of Pawlow, that the
mucous membrane of the intestine secretes a substance, enterokinase,
which activates the trypsinogen of the pancreatic juice, or to the observa-
tion made in the case of the hemolysins by Bordet and Ehrlich, that
this process requires two different substances, — the so-called comple-
ment and Zwischenkoerper."
All these facts show that the production of C02 in the body may
occur without the presence of free oxygen, that these processes are
evidently accelerated by special enzymes.
In regard to the energetics of these processes, it may be said that
the energy which can be obtained by the complete oxidation of dextrose
is about ten times as large as that which can be obtained from it by
alcoholic fermentation. Bunge has calculated that it would not be
possible for a man to do the average amount of muscular work at the
expense of energy derived solely from the alcoholic fermentation of
sugar. For this process the oxidation of dextrose is necessary, and
therefore the presence of oxygen is required.
* O. Cohnheim, Hoppe-Sey lev's Zeitsch. fur physiol. Cheniie, Vol. 39, p. 336, 1903.
24
DYNAMICS OF LIVING MATTER
5. Concerning the Theory of Enzyme Action
a. Stereochemical Attempts.
Liebig expressed the idea that ferments or catalytic substances,
in general, were bodies in a process of decomposition, and that their
condition of motion was communicated to the fermentable body.
Schoenbein, Pasteur, and Traube showed the untenability of this view
by pointing out that platinum or the yeast cell cannot be well considered
as bodies in a condition of rapid decomposition. To-day we do not
value it so highly if an author tries to explain phenomena by vague
statements concerning the vibration of atoms. Now and then an author
still makes the statement that "life is motion," but as Driesch has
pointed out, this statement is about as valuable as the information that
the philosopher Kant was a vertebrate.
Certain observations by Pasteur and Emil Fischer seemed, for a
time at least, to arouse the hope that the theory of enzymatic action
might be found in the field of stereochemistry. Pasteur had observed
in the beginning of his scientific career that while the right-handed
tartaric acid is easily decomposed by fermentation, the same was not
true for left-handed tartaric acid. Pasteur assumed that the geometri-
cal shape of the tartaric acid molecules exercises an influence upon the
fermentability of their solution. From the point of view of stereo-
chemistry the forms of the right- and left-handed tartaric acid molecules
show the same relation of symmetry as our right and left hand, or some
asymmetrical object and its mirror image. It appears from Pasteur's
biography that he expected important discoveries to be made concern-
ing the nature of life from this relation between the form of the asym-
metrical molecules and their biological effect. Pasteur's discovery
found little consideration until it was taken up by E. Fischer* He
found that the alcoholic fermentation through yeast, e.g. Saccharomyces
cerevisicE, depends upon the molecular constitution and configuration
of the various sugars. Saccharomyces cerevisice brings about an
alcoholic fermentation only with triose and hexose, possibly also with
nonose. Tetrose, pentose, heptose, and octose undergo no alcoholic
fermentation with this form of yeast. It is evident that only those
monosaccharides are fermentable by yeast which have three or a
multiple of three atoms of carbon in the molecule. As far as the influ-
ence of the stereochemical configuration of the sugars and glucosides
upon their fermentability is concerned, a similar relation as that found
by Pasteur exists. Of the hexoses or hexaldoses there exist sixteen
* E. Fischer und Thierfelder, Berichte der deutsch. chem. Gesellsch., Vol. 27, pp. 2036 and
2985, 1894. Fischer, Zeitsch. fur physiolog. Chemie, Vol. 26, p. 60, 1898.
GENERAL CHEMISTRY OF LIFE PHENOMENA 25
stereoisomeres, of which, however, only three are fermentable by
Saccharomyces cerevisice, namely, (/-glucose, (/-mannose, and (/-galactose.
The relation between fermentability and configuration will be rendered
a little clearer by the following diagrams : —
H H OH H
1. CH2OH C C C C COH ^-glucose (fermentable)
c c
OH OH
C C COH
H OH
OH OH
C C
H H
H OH
C C COH
OH H
2. CH2OH C C C C COH /-glucose (nonfermentable)
H H OH H
H H OH OH
3. CH20H C C C C COH ^-mannose (fermentable)
OH OH H H
HO HO H H
4. CH20H C C C C COH /-mannose (nonfermentable)
H H OH OH
H OH OH H
5. CH2OH C C C C COH ^-galactose (fermentable)
OH H H OH
etc.
Fischer gave a metaphorical illustration of these facts which was
taken rather literally by some biologists, and which has had a decided
influence upon the formation of biological hypotheses. For this reason
it may be mentioned here. "Inasmuch as the enzymes are in all proba-
bility proteins, and inasmuch as the latter are formed synthetically from
carbohydrates, it is probable that their molecules also have a dissym-
metrical structure, and one whose dissymmetry is, on the whole, com-
parable to that of hexoses. Only if enzyme and fermentable substance
have a similar geometrical shape can the two molecules approach each
other close enough for the production of a chemical reaction. Meta-
phorically we may say that enzyme and glucoside must fit into each other
like key and lock."
Max Cremer* has expressed the idea that in all these cases in reality
one and the same sugar undergoes alcoholic fermentation; namely,
(/-glucose. It is, indeed, not impossible that the alcoholic fermentation
of (/-mannose and (/-galactose occurs in two stages, the first stage con-
sisting in the transformation of these two substances into dextrose. This
would be in harmony with the observations concerning the alcoholic
fermentation of disaccharides, e.g. cane sugar, which must first be
* Max Cremer, Zeitsch. filr Biologie, Vol. 32, p. 49, 1895.
26 DYNAMICS OF LIVING MATTER
hydrolized into dextrose and laevulose by a special enzyme, namely,
invertase. The dextrose and laevulose undergo alcoholic fermentation
by zymase. It has indeed been shown by Lobry de Bruyn that ^-man-
nose, ^-galactose, and ^-fructose can easily be transformed into
dextrose. If this view is correct, the relation between stereochemical
configuration and fermentability is only an apparent one.
b. The Theory of Intermediary Reactions.
The facts that the catalyzer is unaltered at the end of the reaction,
and that apparently a small quantity of the enzyme can catalyze infi-
nitely or comparatively large quantities of the fermentable substance,
harmonize with the assumption of intermediary reactions. As an
example of the theory of intermediary reactions of enzymes, the oxida-
tion of sulphurous acid to sulphuric acid in the presence of nitric acid
may be mentioned. Without the presence of nitric acid, sulphuric acid
is oxidized but slowly ; but in the presence of nitric acid the latter gives
off oxygen to the sulphurous acid, and afterward takes up oxygen
again. The intermediary processes seem to be rather complicated and
are perhaps not fully known, but it seems that the successive transfer
of oxygen from the nitric acid to the sulphurous acid and the reoxida-
tion of nitrous acid to nitric acid occur with much greater velocity than
the direct oxidation of sulphurous acid by free oxygen.
Inasmuch as the chemical nature of the enzymes is unknown, it is
impossible to ascertain positively whether or not their efficiency is due
to intermediary reactions. But there are inorganic catalyzers whose
action resembles that of the enzymes, e.g. platinum and other metals,
like iridium, osmium, silver, etc. We have already mentioned the fact
that platinum acts like lipase in the hydrolysis of ethylbutyrate. The
oxidation of alcohol to acetic acid is accelerated by Bacterium aceti
as well as by platinum.* A striking analogy between the catalytic action
of platinum and enzymes exists in regard to hydrogenperoxide. O. Loew
has shown that there is a specific enzyme catalase, which is very general,
and which accelerates the decomposition of H202. If this decomposi-
tion occurs in the presence of oxidizable substances, the latter, too, are
often oxidized. As a rule the process is represented by the equation —
H202 = H20 + O
The free atom of oxygen is said to be responsible for the oxidizing action
of H202, although Kastle and Loevenhart have expressed a different
view.f They quote a number of observations made by previous authors,
* Bredig enumerates these analogies in his interesting pamphlet on " Anorganischi
Fermente" Leipzig, 1901.
t Kastle and Loevenhart, Am. Chem. Journal, Vol. 29, p. 563, 1903.
GENERAL CHEMISTRY OF LIFE PHENOMENA 27
which indicate that H202 is capable of adding itself to a large number
of compounds and forming bodies like the following: Ba02H202 or
K2022 H202. Jones and Carroll found that certain acids and salts
show in water with solutions of H202 an abnormal depression of their
freezing point. They conclude that in this case a combination between
the molecules of the salts and the H202 is formed. From this and similar
observations Kastle and Loevenhart draw the conclusion that those
substances which like platinum accelerate the decomposition of H202,
first combine with H202, and that this combination is unstable and rapidly
falls apart into molecular oxygen, water, and the catalyzer, i.e. platinum.
If this occurs in the presence of reducing bodies which do not act directly
on H202, they may be oxidized in this process. The platinum may
afterwards combine again with another molecule of H202, and the
process be repeated.
These views find a nice confirmation through the investigation of
the action of certain poisons like HCN on the decomposition of H202
by platinum or catalase. It is well known that HCN kills warm-blooded
animals rather rapidly under the symptoms of lack of oxygen. Schoen-
bein had already shown that prussic acid inhibits the decomposition of
H202 through animal tissues (or the catalase contained in them). Gep-
pert showed that HCN prevents them from consuming the free oxygen,
hence the animals die under symptoms of asphyxiation. HCN prevents
also the decomposition of H202 through platinum. Bredig has con-
tinued the experiments of Schoenbein. As the velocity of the catalytic
action of platinum must be in proportion to the surface of the metal,
Bredig, in order to get a maximal surface, made colloidal solutions of
platinum and other metals. He showed that extremely small doses
of HCN are sufficient to prevent the catalytic action of colloidal platinum
upon H202. Kastle and Loevenhart made it probable that this "toxic"
effect of HCN upon the catalytic action of platinum upon H202 is deter-
mined by the fact that platinum forms an insoluble combination with
HCN. The formation of a film of this insoluble compound on the
surface of the platinum prevents the latter from forming the unstable
combination with H202 which must precede the decomposition of the
latter. The reason why so little of the poison is required for this effect
is due to the fact that the film which is formed on the surface of the
metal may be infinitely thin. Kastle and Loevenhart were able to
put their hypothesis to a test. Silver and thallium act much like plati-
num upon the hydrogenperoxide, inasmuch as both accelerate its decom-
position. While silver forms a combination with HCN which is insoluble
in water, thallium forms a soluble combination. Kastle and Loeven-
hart showed that while hydrocyanic acid inhibits the decomposition
28 DYNAMICS OF LIVING MATTER
of H202 by silver, the catalytic action of thallium upon H202 is not
diminished by HCN.*
The same authors could show, in general, that the anions of those
salts which form insoluble compounds with the metal diminish also the
catalytic action of this metal, while the same salts have no inhibiting
effect if the catalyzer is a metal which forms soluble compounds with
the anion of the salt.
Kastle and Loevenhart found that certain salts accelerate the action
of platinum on the decomposition of hydrogenperoxide. They are
inclined to assume that this class of salts acts directly upon the H202,
and not upon the catalyzer.
Everything seems to indicate that the enzymes accelerate the reac-
tions in the body by forming intermediary, unstable combinations with
the bodies whose reactions they accelerate. These unstable compounds
are rapidly decomposed, and this makes the catalyzer free to repeat the
action. This makes it clear that a small quantity of the catalyzer can
decompose indefinite quantities of the substance. The fact that many
enzymes act specifically also harmonizes well with this view. The
enzymes, being themselves organic compounds of a complex character,
will not form unstable compounds equally well with any organic com-
pound.
Inasmuch as the enzymes are necessary for the chemical processes
in living matter, the formation of enzymes is one of the essential
functions living matter has to perform. Spitzer and Friedenthal were
inclined to assume that the nucleo-proteids act as enzymes. This
view, while possible, is not yet proven.
* Kastle and Loevenhart, Am. Chem. Journal, Vol. 29, p. 397, 1903.
LECTURE III
THE GENERAL PHYSICAL CONSTITUTION OF LIVING MATTER
i. The Limits of Divisibility of Living Matter
The preceding lecture has shown that living matter is a mixture of
various compounds, namely proteins, fats, carbohydrates, and salts. The
fact that the reaction velocity for a number of oxidative and hydrolytic
processes is so great, in spite of the low temperature and the practically
neutral reaction of the tissues, has found its explanation through the
presence of specific enzymes and the intermediary reactions determined
by them. If we ask whether it would suffice for the purpose of making
living matter to try to find a mixture of the above-mentioned substances,
including the enzymes, the answer would have to be no, for the reason
that living matter is characterized by another peculiarity not yet men-
tioned, namely, a definite structure.
Whatever may be the physical structure of living matter, it is certain
that in most cases its complete destruction means the cessation of life
phenomena. A brain or kidney which has been ground to a pulp is no
longer able to perform its functions; yet it is evident from the facts
mentioned in the previous lecture that certain chemical functions can
still be performed by such pulps, e.g. the catalytic processes. The
question now arises as to how far the divisibility of living matter can be
carried without interfering with its functions. Are the smallest particles
of living matter which still exhibit all its functions of the order of magni-
tude of molecules and atoms, or are they of a different order? The
first step toward an answer to this question was accomplished by Moritz
Nussbaum,* who found that if an Infusorian be divided into two pieces,
one with and one without a nucleus, only the latter will continue to live
and perform all the functions of self-preservation and development
which are characteristic of living organisms. This shows that not
only more than two definite substances, but two different structural
elements, are needed for life. We can understand partly from this
why an organ after being reduced to a pulp, in which the differentia-
* Nussbaum, loc. cit.
29
30
DYNAMICS OF LIVING MATTER
tion into nucleus and protoplasm is definitely and permanently lost,
is unable to accomplish its functions.*
The observations of Nussbaum and those who repeated his experi-
ments showed that although two different structures are required, not
the whole mass of an Infusorian is needed to maintain its life. I tried
to solve the question as to how small a fraction of the original cell must
be preserved in order to maintain life in the sense of the definition
given at the beginning of these lectures. Will the smallest possible
element be of the order of an aggregate of a few molecules, or will it
be of the order of a small fraction of the original mass ? I tried to decide
this question in the egg of the sea urchin, immediately after its fertiliza-
tion. The egg divides and reaches successive larval stages, first a blas-
tula, then a gastrula, and finally a pluteus stage. Without especial
efforts the eggs cannot be raised beyond this stage in the laboratory.
I had found a simple method by which the unsegmented eggs of the
sea urchin (Arbacia) can easily be divided into smaller fragments.
When the egg is brought from five to ten minutes after fertilization
(long before the first segmentation occurs) into sea water which has
been diluted by the addition of an equal part of distilled water, the
egg takes up water and the membrane bursts. Part of the protoplasm
then flows out, in one egg more, in another less. If these eggs are after-
ward brought back into normal sea water those fragments which con-
tain a nucleus begin to divide and develop. f In this case the degree
of development such a fragment reaches, is clearly a function of its
mass; the smaller the piece, the sooner on the whole its development
ceases. The smallest fragment which is capable of reaching the pluteus
stage possesses the mass of about one eighth of the whole egg. Boveri
has since stated that it was about one twenty- seventh of the whole
mass. Inasmuch as only the linear dimensions are directly measurable,
a slight difference in measurement will cause a great discrepancy in
the calculation of the mass.
These results are in harmony with experiments made by Driesch %
for a different purpose. Driesch isolated the first blastomeres of the
segmented egg of a sea urchin by shaking the egg and thus bursting
its membrane. He found that an isolated cell of the two- or four-cell
stage of the egg of a sea urchin is still capable of developing into a
normal pluteus, but that an isolated blastomere of the eight- or sixteen-
cell stage no longer possesses this power. This experiment, however,
* It must not be overlooked that in bacteria and the blue algse no distinct differentia-
tion into nucleus and protoplasm can be shown. To these organisms, therefore, the experi-
ments of Nussbaum cannot be applied.
t Loeb, Pfl'uger's Archiv, Vol. 55, p. 525, 1893.
% Driesch, Zeitsch. fur wissenschaftlische Zoologie,Vo\. 53, 1891.
GENERAL PHYSICAL CONSTITUTION OF LIVING MATTER 31
cannot be used as an unequivocal answer to our question, inasmuch
as the possibility exists that in later stages of segmentation the different
cells undergo different chemical changes, whereby they no longer remain
equal in quality.
If we raise the question why such a limit exists in regard to the
divisibility of living matter, the answer is possibly given by Boveri's
observation that the unsegmented egg of the sea
urchin (Strongylocentrotus lividus) possesses three
different layers* It is possible that these three
layers contain chemically different material, and
that only those fragments of an egg are capable
of development which contain material of each
of the three layers. If this be correct, it will
certainly not suffice to mix the chemical con-
stituents of the egg in order to produce the
- , 7 i_ 4 Fig. 6. — After Boveri.
phenomena of development; but we must pro-
vide for a definite arrangement or structure of ^py^^t
this material. We shall see later on that this %%£ ZL**S £■
structure may be very simple and capable of tinct layers.
a physicochemical definition. The limits of
divisibility seem therefore to depend upon the physical structure of
the cells or organs. These limits vary for different organisms and
cells. The smallest piece of a sea-urchin egg that can reach the plu-
teus stage is still visible with the naked eye, and is therefore consider-
ably larger than bacteria or many algae, which also may be capable
of division.
2. Foam Structures and Emulsions
Living matter seen through the microscope invariably offers the
same characteristic appearance which has caused biologists to desig-
nate it with one general term; namely, protoplasm. Yet the common
physical features of living "protoplasm" are still a matter of contro-
versy. Some authors maintain that the protoplasm is a network of
fine fibers, while others say, and apparently justly, that the network
does not occur in living protoplasm, but is caused by the coagulation
of the colloids contained in the cells and liquids of the tissues. It is
a fact that the proteins which are dissolved in the living body are pre-
cipitated by the fixing reagents of the histologists, and when they are
precipitated they form net structures which do not exist during life
when the proteins are held in solution, f
* Boveri, Die Polaritat des Seeigeleies. Verhandl. der physik.-med. Gesdhch., Wurzburg,
Vol. 34, 1901. ' t Hardy, Jour, of Physiology, Vol. 24, p. 158, 1899.
32 DYNAMICS OF LIVING MATTER
Butschli * has expressed a view concerning the structure of living
protoplasm which is more probably correct than the assumption of the
net structure. According to him, living protoplasm has the structure
of a microscopic emulsion. His view is shared by E. B. Wilson and
other authors, while it is accepted, but not unconditionally, by Hardy
and Pauli. Biitschli's conception, however, seems to harmonize with
a great many facts, and therefore we may discuss some features of the
theory of emulsions. Emulsion and foam are, according to Quincke,
only different names for the same (diphasic) physical system. An
emulsion like milk consists of a large number of spherical droplets of
fat, which are distributed in a watery liquid. f We speak of a foam in
the case of an emulsion of a gas in a liquid. The foam in a soap solu-
tion consists of spherical masses of air which are distributed in a watery
liquid. Foams and emulsions have therefore the same physical struc-
ture. The peculiarity of emulsions and foams which interests us in
this connection is their durability, and the theory of foams is concerned
with this side of the problem. According to Lord Rayleigh, an ab-
solutely pure liquid cannot form a durable foam. J When a gas bubble
rises in pure water it is surrounded by a liquid film which, however,
does not possess any durability, and therefore bursts. If, however,
the water is contaminated by another substance, these liquid films
become more durable. This influence upon the durability varies with
the nature of the contaminating substance. It is known that the addi-
tion of small quantities of colloidal material, e.g. soap, saponin, a solu-
tion of gelatine, is capable of making the liquid films very durable.
This influence of the contamination is due to its effect upon surface
tension. Experiments have shown that those substances which make
these liquid films more durable decrease the surface tension which ex-
ists at the limit between water and the emulsified substance. In con-
sequence of this latter fact, these substances have a tendency to collect
at the common surface between water and air, or whatever the emulsi-
fied substance may be. The surface acts like a trap on such particles,
inasmuch as it requires an outside force to bring them back to the
interior, if they have once collected at the surface. § The consequence
is that a film of this contaminating material is formed at the surface,
between the water and the oil droplets, or whatever the substance held in
emulsion may be. In the case of oil emulsions in water, the contami-
nating substance is a trace of soap formed through the hydrolysis of fat
* Biitschli, Untersuchungen uber microscopische Sch'dume und das Protoplasma, Leipzig,
1892.
1 Quincke, P/Zuger's Arckiv, Vol. 19, p. 129, 1879.
% Lord Rayleigh, Scientific Papers, Vol. 3, p. 351, 1 902.
§ F. G. Donnan, Zcitsch. fur physikal. Chemie, Vol. 31, p. 42, 1899.
GENERAL PHYSICAL CONSTITUTION OF LIVING MATTER 33
or oil. Soap solution diminishes the surface tension between water and
oil. The question arises as to how this circumstance can make the
emulsion more durable. The answer is as follows : If a film of water
separates two oil drops, the soap particles gather at the surface on
either side of the water film. If these soap particles be now brushed
aside on one spot of this watery film, the water will come in direct con-
tact with the oil. The surface tension between oil and water is greater
than that between soap solution and water. Hence, in a spot where
the soap is removed the surface tension or tendency to contract will
be greater than in the rest of the film, and the consequence will be that
this spot will contract and thus mend the hole in the layer of soap. In
this way the diminution of the surface tension by the contaminating
substance makes the emulsion more durable, and prevents the fusion
of two neighboring droplets in an emulsion. It is not impossible that
the existence of such a film may explain why it is that the cleavage ceils
of an egg do not easily fuse.
As far as the thickness of the contaminating layer is concerned,
Lord Rayleigh has measured it, and found that the contaminating
layer of oil on the surface of water which suffices to prevent the motion
of particles of camphor on the surface of water, need be only ysoWoo"
mm. thick. It is hardly necessary to mention that such a film is far
below the limits of microscopic visibility.
Butschli assumes that living protoplasm is an emulsion of two
liquids : a viscous one, which is insoluble in water ; and a watery liquid,
which possesses little viscosity.*
3. The Colloidal Character of Living Matter
Hardy as well as Butschli assumes that living matter is essentially
liquid. The most common observations on living organisms, which
are sufficiently transparent, show that this is undoubtedly true for a
large part of the material contained in such organisms. Certain ele-
ments, however, are apparently solid, e.g. the surface films of cells and
nuclei, and possibly certain structures in the interior of the cell, such
as centrosomes. The observations of Traube, as well as Hardy, show
how solid constituents can be formed from liquids in living matter.
We are dealing here with a chapter of the physics of colloids, which
is just at present the object of many investigations.
The substances in living matter which occur in a liquid as well as
in a solid condition are the colloids. The name was given by Graham,
who discriminated between two kinds of soluble substances, — crystal-
* Biitschli, Archiv fur Entwickelungsmechanik, Vol. 11, 499, 1901.
D
34 DYNAMICS OF LIVING MATTER
loids and colloids. The former diffuse easily through animal mem-
branes, the latter only with difficulty, or not at all. It is, however,
well to remember that there exist transitions between both groups.
According to Krafft,* the colloidal character of sodium soaps increases
with the size of the acid molecule. Thus sodium acetate possesses
the qualities of a crystalloid in a watery solution, while sodium stearate
belongs to the colloids. The proteids, certain carbohydrates like
starch or glycogen, and higher fats, belong to the colloids; while their
products of cleavage, e.g. dextrose, may belong to the crystalloids.
According to Krafft, there is therefore a steady transition from the
crystalloids to the colloids, f
In physical chemistry, as a rule, a different idea of the colloidal
solution is given, i.e. that they are no real solutions, but suspensions
of small particles in a liquid, or a system of two phases. We have
already mentioned the fact that not only organic substances may form
colloidal solutions, but also many inorganic substances, and even pure
metals, such as platinum, gold, silver, etc. All these colloidal sub-
stances alter the freezing point or boiling point of the liquid not at all
or but little. From this the conclusion is drawn that no work, or but
little, is required to separate the solvent from the dissolved colloidal
particles. It must, however, be stated that according to some authors
the proteins dissolved in the blood serum have a definite osmotic pres-
sure which is far from being a " quantite negligeable." Starling J found
by a direct measurement — the freezing-point determinations fail in
such cases — an osmotic pressure of the colloids of as much as 30
to 40 mm. of mercury. This pressure plays, according to Starling,
a definite and important role in phenomena of lymph formation, oedema,
etc. In view of Starling's observations it is doubtful whether we still
have a right to maintain that colloidal solutions behave like suspensions,
inasmuch as the latter differ from real solutions through the fact that
they possess no measurable osmotic pressure.!
A second argument in favor of a principal difference between col-
loidal and crystalloidal solutions lies in the fact that dissolved particles
in a colloidal solution have, as a rule, a definite electrical charge. The
same is often found in the particles which form suspensions in water.
The existence of the electrical charge can be demonstrated if an
* Krafft, Zeitsch. fur physiologische C/iemie, Vol. 35, pp. 364 and 376, 1902.
t This idea receives still further support from the fact that if a salt solution is exposed
to the action of a centrifuge, the concentration at the periphery becomes larger than at the
center.
J Starling, Jour, of Physiology, Vol. 19, p. 312, 1895.
§ More recently Reid has reached the conclusion that the colloids in Starling's experi-
ments were not free from salts, and that he in reality measured the osmotic pressure of the
latter.
GENERAL PHYSICAL CONSTITUTION OF LIVING MATTER 35
electrical current be sent through a colloidal solution; in this case, the
particles move in the direction of the negative or positive current, ac-
cording to the chemical character of the colloid. This charge of the
colloidal particles is generally held to be due to the formation of a
double layer of electricity at the surface, between particle and water. A
similar explanation was given to the charge of particles suspended in
water; and this is considered another argument in favor of the idea,
that colloidal solutions are diphasic systems. It is, however, possible,
as Freundlich * has already mentioned, that the charges of the col-
loidal particles are due to the electrolytic dissociation of the latter. It
had generally been noticed that the colloids of an acid character are
negatively charged when in solution, while colloids of an alkaline char-
acter are positively charged. This is exactly what should be expected
if the charges of the colloidal particles in solution are due to electro-
lytic dissociation. If the colloid is an acid, it will dissociate into one
or more positively charged hydrogen-ions and a negatively charged
colloid-ion; if the colloid is an alkali, it will dissociate into one or
more negatively charged hydroxyl-ions and a positively charged
colloid-ion.
Hardy f has shown that dialyzed white of egg (from the white of
a hen's egg) is electro-positive when a trace of acid is added, while a
trace of alkali makes it electro-negative. He believes that in the for-
mer case, the hydrogen-ions are caught in the meshes of the colloidal
particles of the white of egg and carry the latter with them when they
migrate in an electrical field. When alkali is added, the hydroxyl-
ions are caught in the meshes of the particles and drag the latter with
them in an electrical field. I have called attention % to the fact that
Hardy's observations allow of a different interpretation, namely, that
they may be due to the electrolytic dissociation of the white of egg.
The proteins have an amphoteric character, i.e. they are able to give
off HO-ions, as well as H-ions, to the surrounding solution. If we add
a trace of acid to the solution of dialyzed white of egg, the degree of
dissociation of the acid part of the molecule is diminished, and it will
dissociate chiefly into HO-ions and a colloid cation, and the latter will
migrate in an electrical field to the cathode. If a trace of alkali, how-
ever, is added to the surrounding solution, for the same reason, the
white of egg will be prevented from sending as many HO-ions into
solution as H-ions, and the molecule will dissociate mainly into H-ions
and a colloid anion. Hence, the addition of a trace of acid will give
* Freundlich, Zeitsch. fur physikal. Chemie, Vol. 44, 1903.
f Hardy, Proceedings of the Royal Society, Vol. 66, p- no, 1901.
j Loeb, University of California Publications, Vol. 1, p. 149, 1904.
36 DYNAMICS OF LIVING MATTER
the colloidal particles a more positive charge, while a trace of alkali
will give them a more negative charge.
Hardy was the first to call attention to the fact that the electrical
charge of the colloidal particles — or, in his opinion, the difference of
potential between the particles and the surrounding solution — is a
prerequisite for the stability of many colloidal solutions.* If in these
solutions the charges are removed from the particles, a precipitation
occurs through the clumping together of the small colloidal particles
to larger aggregates and the falling of these aggregates. Hardy
proved this in two ways: first, by carefully neutralizing acid white
of egg with NaHO, until the particles no longer migrated with the
positive or negative electric current. As soon as this occurred, a
slight mechanical agitation of the particles was sufficient to produce a
precipitation of the white of egg. The second proof consisted in show-
ing that when a constant current is sent through the solution, the par-
ticles that are carried to the electrode are precipitated. At the pole
the particles lose their charge and become isoelectric with the surround-
ing water. It is, however, not impossible that acid or alkaline white
of egg is soluble, while the neutral white of egg is insoluble, or less
soluble, in water.
It had been known for a long time that water which was rendered
opaque through a suspension of small particles could be made clear
if salts were added to the suspension. A similar experience had been
made in connection with the precipitation of colloidal particles. It
was further known that the precipitating power of various electro-
lytes is a function of only one of the two ions, — mostly the cation, —
and that it increases with the valency of the active kind of ions. The
fact that Freundlich found in experiments with a sol of arsenic sulphide,
whose particles have a negative charge, that the precipitating force of
salts with a bivalent cation was about seventy times as large as that
of salts with a univalent cation, while salts with a trivalent metal pos-
sessed a precipitating force five hundred times as large as that of a uni-
valent cation, may serve as an example. Hardy added the important
fact that in the case of sols with negatively charged particles, the pre-
cipitation is due to the cations; while in the case of positive colloids
the precipitation is caused by the anions of the precipitating salt.
Hardy states that the precipitating power of an ion is an exponential
function of its valency.f Freundlich, however, has shown clearly
that where the cation of a salt causes the precipitation, the anion is
not without some effect. It seems quite possible that the facts found
by Hardy indicate a purely chemical action of the precipitating salt.
* Hardy, loc, cit. f Hardy, Jour, of Physiology, Vol. 24, p. 288, 1899.
GENERAL PHYSICAL CONSTITUTION OF LIVING MATTER 37
A negatively charged colloid can form salts with metals; and it is in
harmony with the general facts concerning the solubility of salts, that
the latter decreases with the valency of the ion with which the colloid
combines. Hardy, Bredig, and many other authors believe, however,
that in this case the ions act only through their electric charges. Hardy
has recently found that electro-negative globulin solutions are rapidly
precipitated by the positive electrons sent out by radium.* It is pos-
sible that the radiation, in this case, causes a precipitation only in-
directly, while its direct action is a chemical change in the globulin
solution.
If we accept the view of Hardy and Bredig, that we are dealing in
the action of sols with an effect of an electrical charge of the ions, we
shall do well to adopt Bredig's "j" explanation of this effect. The sur-
face tension at the limit of two media reaches a maximum, when the
difference of potential between the two media becomes a minimum.
This is due to the fact that the electrical charges are antagonistic to the
surface tension. The higher the surface tension between colloidal
particle and surrounding liquid, the easier will the slightest agitation
cause a clumping of the smaller particles into larger aggregates. Those
who hold this view have thus far not yet shown how it happens that
the valency of an ion has so great an effect upon the precipitation of
the colloidal particles, although each precipitating salt carries equal
quantities of positive and negative charges into the solution.
Not all the colloidal solutions show cataphoresis. Hardy men-
tions that globulins which are held in solution by salts do not migrate
when a constant current passes through them.
Life depends upon the existence of these colloidal solutions in the
cells. All agencies which bring about a general gelation, bring life
to a standstill; and such a standstill is permanent in case irreversible
gels are formed, such as originate if proteins are heated. The liquid
proteins of our body coagulate at a comparatively low temperature,
and this is the reason that at a temperature of about 45 ° the cells of
our . body die very rapidly. The heavy metals also transform the
proteins of our body into irreversible gels, and this may be a reason
why tliey are so poisonous. There are, however, conditions in
which the transformation of sols into gels does not lead to death,
but to the formation of important morphological structures, e.g. Traube's
membranes of precipitation. The astrospheres also originate, accord-
ing to the botanist, Alfred Fischer, through a process of coagulation.
It is, moreover, possible that a series of manifestations of life in cell-
* Hardy, Jour, of Physiology, Vol. 29, p. xxx, 1903.
f Bredig, Anorganische Fermente, Leipzig, 1901.
38 DYNAMICS OF LIVING MATTER
division and protoplasmic motion, rhythmic contractions, etc., depend
upon alternating gelations and liquefactions. It is, however, useless
to discuss such possibilities until more definite proofs of their real ex-
istence have been furnished. Such proofs thus far exist only in regard
to membranes of precipitation.
4. The Formation of Surface Films and Traube's Membranes
of Precipitation
It is a general rule that every free cell is surrounded by a solid film.
The pseudopodia of many Infusorians could not exist were they entirely
liquid. Liquid circular cylinders begin to fall apart into droplets as
soon as their height becomes greater than the periphery of their base.
The length of the pseudopodia of rhizopods is, however, very often a
multiple of their circumference. As the interior of the pseudopodia
shows phenomena of streaming, the solid part of the pseudopodia can
only be at their surface. Such solid surface films may be exceedingly
thin, according to Quincke's observations.
Ramsden has recently shown why masses of protoplasm must form
solid films at their surface. He had formerly observed that the white
of a hen's egg can be caused to coagulate by mere mechanical agita-
tion.* The explanation of this fact was subsequently found in the fur-
ther observation, that without any evaporation at the free surface of
the protein solutions, solid or extremely viscous films are formed very
rapidly. t If such solid particles be removed from the surface, i.e. by
mechanical agitation, new particles will come to the surface and form
membranes. This is in harmony with what was stated earlier in regard
to the gathering of contaminating particles at the surface between two
media.
What has been said here with reference to the formation of solid
films at the surface of free cells, may also hold with regard to the for-
mation of solid films at the surface of nuclei.
Traube has shown that where two liquid colloids come in con-
tact, solid membranes may be formed. He investigated the mechanism
of the formation of the membranes of plant cells and was led to the
conclusion that the formation of these membranes, and the peculiarity
of the cell to grow, depend upon a simple physical process. Certain
colloids form a precipitate where they come in contact with each other,
and this precipitate is impermeable for either colloid. The precipitate
must therefore assume the shape of a thin film, which prevents the
* Ramsden, Archiv fur Anatomie und Physiologie, Physiologische Abteilung, p. 517, 1894.
t Ramsden, Zeitsch. fur physik. Ckemie, Vol. 47, p. 336, 1904.
GENERAL PHYSICAL CONSTITUTION OF LIVING MATTER 39
further action of the two colloids upon each other. He called this film
the membrane of precipitation.* The following example may be quoted :
"A solution of a certain gelatine — • /3-gelatine — was prepared, and a
drop taken out of this solution with a glass rod. The drop remained
hanging at the end of the rod, and was exposed to the air for several
hours; it was then dipped in a 5 per cent solution of tannic acid. In
about ten minutes a thin iridescent solid film formed at the surface of
the drop. The /3-gelatine and the tannic acid had formed a membrane
of precipitation at the common surface, which was impermeable for
both colloids and thus prevented any further reaction between the two."
But it is not necessary for the formation of membranes of precipitation
that two colloids act upon each other. A crystalloid and a colloid may
form a membrane of precipitation, as is the case when a drop of tannic
acid is dipped into a neutral solution of lead acetate. Two crystal-
loids can also form such membranes if they only form an amorphous
precipitate which is impermeable for both crystalloids, e.g. ferrocyanide
of potassium and ferric chloride. While these membranes are imper-
meable for certain substances, they are not so for others ; and Traube
recognized the fundamental importance of this fact for life phenomena,
"The cell membrane! makes a diminutive chemical factory of the con-
tents of this cell by shutting it off from its surroundings, and enables
each cell to lead a specifically different life from the neighboring cells."
The substances which can permeate the membranes of precipitation
vary according to the nature of the latter. All of them allow water to
pass through; while they do not allow sugar or salts to pass through
at all or not equally well. Traube pointed out that this semipermea-
bility also explains the mechanism of cell growth. When the drop of
/3-gelatine (or any other substance used for the experiment) had a
greater concentration than the solution into which it was dipped, the
drop began to grow in size as soon as the membrane of precipitation
was formed. Traube thus became the originator of the modern theory
of the growth of cells, which assumes that the growth is caused by the
cell absorbing water in consequence of its osmotic pressure being higher
than that of the surrounding solution.
Traube was inclined to explain the semipermeability of his artifi-
cial membranes on the basis of the assumption that they possess very
small pores or interstices which allowed only small molecules, such as
water, to permeate; while the larger molecules, such as salts, could
not pass through them. This assumption was no longer tenable after
* M. Traube, Reicherfs und Du Bois Raymond's Archiv, 1867. Gesammclte Abhand-
lungen, p. 213, Berlin, 1899.
t We should now say, the surface film of protoplasm.
40 DYNAMICS OF LIVING MATTER
Overton found that the alcohols, even those having large molecules,
could pass into the cells much more readily than the salts with smaller
molecules. Nernst had given another theory of semipermeability
which is generally accepted; namely, that the substances which go
through the semipermeable walls must first be dissolved in this mem-
brane, and that therefore such substances must be absorbed most
rapidly by these cells as are most soluble in the cell walls, or surface
films of the cells. Overton * found that plant and animal cells which
show the properties of semipermeability are generally most permeable
for those substances which are most soluble in oil or fat, e.g. alcohol,
ether, chloroform. He accepts Nernst's theory and draws the conclu-
sion that the cells, or the protoplasm of the cells, are surrounded by a
film of a fatty substance, such as lecithin or cholesterin, and that these
substances give protoplasm the quality of semipermeability.
A similar conclusion had already been drawn by Quincke, who
had noticed that protoplasm assumes a spherical shape when squeezed
out of its cell into a watery liquid. This, he said, was only intelligible
when protoplasm is surrounded by a film of oil or fat.f Quincke also
pointed out that such films of oil must show the phenomenon of semi-
permeability.
Hans Meyer and Overton % have noticed independently of each
other that all narcotics have one property in common; namely, a
comparatively great solubility in fat, or lipoids like lecithin or choles-
terin. The special importance of this lies in the fact that the narcotic
effect of a substance increases, on the whole, with the degree of its
solubility in fat. They are inclined to believe that the chemical nature
of the narcotic is otherwise of no or only minor importance, as they
find that chemically inactive bodies may be very powerful narcotics,
if only their solubility in oil is comparatively high. It seems to me,
however, that in view of the presence of so many enzymes in our cells,
substances may be very active in our body, which in the absence of such
enzymes may appear rather inert. This does not, however, contradict
the fact that the solubility of narcotics in fat plays a role in the absorp-
tion of narcotics. Those cells in our body which are richest in lipoids,
namely, the ganglionic cells, also feel first the effects of narcotics.
Meyer and Overton assume that the narcotics, such as alcohol,
ether, etc., act merely by altering the physical properties of the cells
in whose lipoids they dissolve. The fact that anaesthetics like ether
and chloroform dissolve fat was utilized for an explanation of their
* Overton, Vierteljahreschrift der naturforschenden Gesellsch. in Zurich, Vol. 44, p. 88,
1899. (The original was not accessible to me.)
f Quincke, Sitzungsberichte der Berliner Akadetnie der JVissenschaften, p. 79*> 1888.
% Overton, Studien iiber die Narcose, Jena, 1901.
GENERAL PHYSICAL CONSTITUTION OF LIVING MATTER 41
physiological action immediately after the discovery of this action.
At that time the various authors, e.g. von Biebra and Harless, ex-
plained the action of ether and chloroform on the assumption that these
substances caused the fat to leave the cells by dissolving it. This does
not seem to harmonize with the fact that a person so soon recovers from
the effects of a narcosis. Overton showed, moreover, that ciliary cells,
when narcotized in water by ether or chloroform, may resume their
activity when brought back into pure water. This would not be pos-
sible if the narcotic effect of ether or chloroform had been due to the
diffusing of fats from the cell; but the fact that a person can recover
from the action of narcotics does not prove that their action is a purely
physical one. A person who becomes unconscious from the lack of
oxygen may also recover, if oxygen is admitted again, soon enough,
and yet no one would conclude from this that the action of oxygen is
purely physical. The rapidity of the absorption of narcotics may be
due to their solubility in oil, and yet the effect they produce may be
due to something entirely different.
5. Osmotic Pressure and the Exchange of Liquids between
the Cells and the Surrounding Liquid
The observations of Traube, Quincke, Ramsden, and Overton
have given us some hints as to the nature of the surface films which
surround protoplasm. Their importance lies in the fact that the con-
tents of the cells are chiefly liquid, and that an exchange of dissolved
substances occurs steadily between these substances and their sur-
roundings. Animal cells are surrounded by a liquid which resembles
sea water in its constitution, though its osmotic pressure is in land and
fresh-water animals, and in some marine animals, less than that of
sea water. The main force for the exchange of dissolved substances
between the cells and the surrounding solution is the osmotic pressure.
Inasmuch as the cells take up the salts, proteins, fats, and carbohy-
drates that are dissolved in the blood, we cannot accept Overton's
view that only water and those substances which are soluble in fat pass
through the membranes, and that salts generally cannot pass through.
We hold that the cell walls are not impermeable to salts, and that there
is only a difference in the rate of diffusion of the various substances,
many salts diffusing only very slowly into the protoplasm. The con-
sequence is that for short experiments the cells act as if they were im-
permeable for salts and permeable for water only. When cells are
put into salt or sugar solutions, whose osmotic pressure is higher than
that of the liquid of the cells, the cell loses water; and in the case of
42 DYNAMICS OF LIVING MATTER
most plant cells a condition ultimately arises in which the protoplasm
becomes separated from the cellulose wall, the so-called plasmolysis.
Nevertheless it cannot be said that plant cells are impermeable for
salts, inasmuch as the building up of the living matter of the plant
depends upon the diffusion of certain salts from the soil into the plant,
e.g. nitrates, phosphates, sulphates, potassium salts, etc. For' the
animal cell this can be demonstrated still more strikingly. The com-
mon striped muscle of the heart loses its excitability rather rapidly
when put into a physiological salt solution to which a certain (but not
too small) amount of KC1 is added; but if the muscle is taken out in
time and put back into a pure NaCl solution, its excitability returns.
The velocity with which the inhibiting effect of the potassium salts
upon the irritability occurs, depends upon the concentration of the
potassium salts in this solution; it is therefore certain that the potas-
sium salts diffuse comparatively rapidly into the muscle and out of it.
The same can be shown for Na, Ca, and many other, if not all salts.
When the muscle is put into an isotonic solution of any sodium salt,
rhythmical contractions begin, and the sooner the higher the concen-
tration of the sodium salts. The same is true for solutions of barium
salts. The velocity with which the sodium salts produce these twitch-
ings varies with the nature of the anion of the salt. If to the solution
of the sodium salt a small but definite quantity of a calcium salt be
added, these contractions are suppressed. These facts are only con-
ceivable if we assume that muscle cells are permeable for Na, Ca, and
Ba salts, or ions. They must, however, be permeable for other salts
also, e.g. Li, Cs, and Rd salts, as they begin to twitch in these solu-
tions.* The more toxic salts, e.g. those of the heavy metals, must also
be able to diffuse into the cells, as otherwise they could not be so
toxic.
The salts diffuse more slowly into the muscle than water. If mus- .
cles be put into salt solutions of various concentrations, it will be ob-
served that during the first hour or hours, the muscle absorbs water
and swells in hypotonic solutions, while it loses water in hypertonic
solutions. This phenomenon is, in wide limits, independent of the
nature of the salt in solution.! If the muscle remains longer in the solu-
tion, however, the influence of the osmotic pressure diminishes, and the
specific effects of the salt appear. I found that in a 0.7 per cent solu-
tion of NaCl, or an equivalent solution of NaBr or Nal, a muscle does
not materially change its weight during eighteen hours. If there is
* Loeb, Festschrift fiir Professor Fick, 1899. Pfliiger's Archiv, Vol. 91, p. 248, 1902.
See also the numerous papers of Ringer in this field of investigation.
t Loeb, Pfliiger's Archiv, Vol. 69, p. 1, 1897; and E. Cooke, Jour, of Physiology, Vol.
23> P- *37> l89§-
GENERAL PHYSICAL CONSTITUTION OF LIVING MATTER 43
an increase in weight, as a rule, it does not exceed 7 per cent of the
initial weight of the muscle. In the corresponding equimolecular
solutions of potassium salts, the muscle increases its weight in the
same time 40 per cent or more, while in an equimolecular solution
of CaCl2, it may lose water, sometimes as much as 20 per cent.* In all
these solutions the weight of the muscle changed but immaterially
during the first hour. These facts become intelligible on the assump-
tion that the salts diffuse into the muscle, although with less rapidity
than the water. As far as the specific action of K, Na, and Ca salts
upon the absorption of water by the muscle is concerned, it is some-
what analogous to the behavior of various soaps. Potassium soaps are
extremely hygroscopic, and absorb water in such quantities as to make
them liquid, while calcium soaps absorb but little water; and sodium
soaps occupy a position between these two. Soaps contain water in
a form in which it can be squeezed out by a slight pressure. The same
is also true for some, perhaps most of the water absorbed by muscles,
and this holds also, according to Van Bemmelen and Hardy, for the
water which is contained in irreversible gels, such as coagulated white
of egg or a gel of silicic acid. Such gels evidently contain the water
in capillary spaces. Evidently the Na-, K-, Ca-ions ultimately bring
about a coagulation in the muscles; but the structure and size or other
physical properties of the interstices in the coagulated material change
with the nature of the metal which brings about the coagulation. This
is further corroborated by putting the muscle into solutions of a salt,
e.g. NaCl, of various concentrations. During the first hour or so the
volume of the muscle changes, as one would expect if the muscle were
permeable for water, but impermeable or little permeable for salts;
but after a longer period a paradoxical result is obtained. In solutions
of higher osmotic pressure than the muscle, the latter increases in
volume and weight, and within certain limits, the more so the higher
the concentration of the solution, as the following table shows: —
_ _T _ „ Increase in Weight of Muscle in Twenty-four
Concentration of the NaCl Solution Hours in Per Cent of its Original Weight
1-05% + 0.7%
1-4% + 6.7%
i-75% +13%
2-1% +17-7%
2.45% +19%
2.8% +23.8%
This experiment might at first suggest that the osmotic pressure is not
the force active in this case ; but this is not true. The osmotic pressure
* Loeb, Pfliiger's Archiv, Vol. 75, p. 303, 1899. (A dead muscle absorbs no water in
a physiological salt solution, thus showing that the above-mentioned effects of K or Ca can-
not be attributed merely to the death of the muscle.)
44 DYNAMICS OF LIVING MATTER
is the active force, but through the slow but gradual entrance of
NaCl into the muscle, and possibly the loss of water and salts, on
the part of the muscle, new conditions for the absorption of water
are created which correspond with Van Bemmelen's observations on
gels.
If a little acid be added to a 0.7 per cent solution of NaCl (which
is about isosmotic with the gastrocnemius of a frog), the gastrocnemius
will absorb considerable quantities of water from such a solution. The
quantity of water absorbed increases with the quantity of acid used.
For inorganic acids it can be shown that the effect is chiefly determined
by the hydrogen-ions, and not by the anions. Organic acids, however,
act considerably stronger than should be expected, if the effect were
purely due to the free hydrogen-ions.* The cause of this anomaly is
not yet known. If, however, acids are added to a hypertonic solution
of NaCl, the effect is the reverse; the acid diminishes the amount of
water absorbed by the muscle.f Alkalis increase the absorption of
water under all circumstances. In these cases the acids and alkalis
act probably through their combination with the proteids, whereby
the conditions for the absorption and giving off of water are changed.
It is therefore obvious that other forces than the mere osmotic pressure
play a role in the absorption of liquids by tissues.
The same seems to be true for the reverse process; namely,
the secretion of liquids from the cells. In these cases work is often
done against the osmotic potential. It is evident that another force
must be at work besides the mere osmotic pressure. The fact discov-
ered by MacCallum, that the same salts which increase the peristaltic
motion of the intestine also increase the secretory action of the glands
of the intestine, % seems to indicate that this force may be of the nature
of the contractile forces. The same salts which increase the secretion of
liquid from the blood into the intestine also increase the secretory
action of the kidneys.
Hober § has recently called attention to another possibility. Ham-
burger had found that acids, e.g. C02, increased the permeability of red
blood corpuscles for certain anions. Hober has shown that such an
increased permeability for anions must lead to a difference of potential
between the inner and outer surface of the semipermeable elements,
the inner surface assuming a positive charge. It is possible that such
differences of potential, in case they lead to an electric current, may
* Loeb, Pfluger's Archiv, Vol. 69, p. 1, 1897 '■> Vol. 71, p. 457, 1898.
f Loeb, Pfluger's Archiv, Vol. 75, p. 303, 1899.
% J. B. MacCallum, University of California Publications, Vol. I, p. 5, 1903; and pp.
81 and 125, 1904. Pfluger's Archiv, Vol. 104, 1904.
§ R. Hober, Pfluger's Archiv, Vol. 102, p. 196, 1904.
GENERAL PHYSICAL CONSTITUTION OF LIVING MATTER 45
bring about a cataphoresis of the water or the particles dissolved in it,
into or out of the cell.
But in view of the observations of MacCallum I am more inclined
to believe that contractile phenomena inside the cell furnish at
least part of the energy of secretion and absorption in those cases
where the osmotic forces alone cannot explain these phenomena. To
illustrate what possible form these forces may assume, I may point
out the rhythmical squeezing out of the liquid contents of the
vacuole in Infusorians. Here the work of secretion is obviously
done by protoplasmic contraction, and not by osmotic pressure. It
is quite possible that, mutatis mutandis, something similar may occur
in all cells, although this is only a surmise.
6. Further Limitations of Traube's Theory of Semipermeability
Traube's idea that all living cells are surrounded by a membrane
which is absolutely permeable for water, does not seem correct for a
number of marine animals. Fundulus heteroclitus, a marine fish,
lives and develops exclusively in sea-water, i.e. in a solution whose
osmotic pressure is, roughly estimated, like that of a half-grammolecular
I — ) solution of NaCl. I have found that this fish as well as its eggs
can be put permanently into distilled water without the least injury.
No swelling of the eggs or the tissues occurs under these conditions.*
It may also be put into sea water whose osmotic pressure has been
increased by the addition of a certain percentage of NaCl without
perceptible shrinkage. This shows that water does not diffuse rapidly
through the skin of the animal or the membrane of the egg. It cannot
be stated, however, that it does not diffuse at all, since it is possible
that a slight diffusion of water into the cells may be compensated by
an increased secretion of water from the cells. In addition, the egg and
animal must be but slighly permeable for salts, as otherwise the salts
would diffuse from the blood and the tissues of the animal into the
distilled water, and this would cause the death of the animal. The
skin and the egg cannot be said to be absolutely impermeable, since gases
like O and C02 diffuse into the eggs, and since the latter rapidly dry
out and die when taken out of the water and exposed to dry air. More-
over, K and other toxic salts are able to diffuse slowly into the egg, as
can be shown by the fact that if potassium salts are added to sea water,
the heart of the embryo soon stops beating.
* Loeb, Pfluger's Archiv, Vol. 55, p. 530, 1893. Am. Jour. Physiology, Vol. 3, pp.
327 and 383, 1900 ; and Vol. 6, p. 411, 1902.
46 DYNAMICS OF LIVING MATTER
The behavior of Fundulus to distilled water is not the rule for
marine animals, as most of them when subjected to it die rapidly. I have
recently made a series of experiments with a marine Crustacean Gam-
marus, of the Bay of San Francisco.* The osmotic pressure of the
sea-water of the bay varies at different times of the year between that
of about an — and a | m NaCl solution. When Gammarus is brought
4
suddenly from bay water into distilled water, its respiratory motions
stop, as a rule, in about half an hour. This standstill becomes per-
manent, unless they are put back into sea water within a short time
(about ten minutes). If, however, Gammarus be put into a cane
sugar, dextrose, or lactose solution of any concentration from — to
8
| m upward, they die just as rapidly, if not more so, than in distilled
water. The same is true when the animals are put into a pure NaCl
solution isosmotic with the sea water. They die still more rapidly
when put into distilled water, to which all the other salts found in the
sea water are added, with the exception of NaCl, and in the concentra-
tion in which those salts occur in sea water. If they are put, however,
into a solution of NaCl, KC1, and CaCl2, in that proportion in which
these salts occur in the sea water, the animals may live as long as forty-
eight hours; and if some MgCl2 is added to this solution, the animals
may live as long as in sea water. If we prepare solutions composed
of only two of the salts contained in the sea water ; namely, NaCl + KC1,
or NaCl + CaCl2, or NaCl + MgCl2, the Gammarus lives only a few
hours. These experiments prove that the medium surrounding the
Gammarus must not only have a definite osmotic pressure, but that
this pressure must be supplied by specific salts. Perhaps the follow-
ing data may explain, in part at least, why this lack of specific salts
leads to the death of the animal.
7. The Antagonistic Effects of Salts
When the eggs of Fundulus are put immediately after fertilization
into a pure solution of NaCl, whose concentration roughly equals that
in which this salt is contained in the ocean, — , or f m, no egg is
able to form an embryo. The eggs begin to segment and may go
as far as the 64-cell stage, but after this they die. But if to the
NaCl solution a small but definite amount of a bivalent metal (with
the exception of the most poisonous ones, like Hg), is added, just as
* Loeb, Pfluger's Archiv, Vol. 97, p. 394, 1903 ; Vol. 101, p. 340, 1904.
GENERAL PHYSICAL CONSTITUTION OF LIVING MATTER 47
many eggs form embryos as in normal sea water.* It is a striking
fact that not only the salts of such bivalent metals which occur in the
sea water or the body, e.g. Ca and Mg, render the pure NaCl solution
harmless ; but also such salts as do not occur in the body, or are posi-
tively poisonous, e.g. Sr, Ba, Co, Zn, Pb, and others. An example will
illustrate these antagonistic effects between the salts of the univalent and
bivalent metals.
Percentage of the Fundulus Eggs
Nature of the Solution *hich form an Embryo in this
Solution
100 c.c. \m NaCl 0%
100 c.c. \ m NaCl + \ ex. — CaS04 3%
64
100 c.c. I m NaCl + 1 c.c. — CaS04 3%
64
100 c.c. § m NaCl + 2 c.c. — CaS04 20%
64
100 c.c. f m NaCl + 4 c.c. — CaSO. 75 %
64
100 c.c. I m NaCl + 8 c.c. ~ CaS04 70%
64
It is remarkable how small a quantity of calcium suffices to render
the NaCl solution harmless. The anion has nothing to do with this
effect of the calcium salt, as the result remained the same when any
other soluble calcium salt was used, e.g. Ca(N03)2 or CaCl2. The
results also remained the same when in the place of the Ca salts, Sr, Ba,
Co, Zn, or Pb salts were used, and even the quantities of the salt required
to make the NaCl solution harmless were about the same for all the
salts. I think it is one of the most striking facts known in toxicology
that a pure solution of NaCl of that concentration in which this animal
lives is poisonous, while this solution can be rendered less harmful or
harmless by adding so poisonous a substance as Ba, Co, Zn, Pb, etc.
If the eggs of Fundulus are raised in a solution of a salt with another
univalent cation than Na, e.g. K, Li, or NH4, we find that beginning with
a certain concentration a solution of each of these salts becomes a poison
for the eggs of Fundulus, that is to say, does not allow any egg to form
an embryo. If, at that concentration of one of these salts, a small but
definite amount of a salt with a bivalent cation is added, the eggs form
embryos and they are able to develop. Trivalent cations, like Al and
Cr, were also able to render the toxic concentrations of salts with a
univalent metal less harmful. The antitoxic effect of a tetravalent
cation, Th, however, was found to be only slight.
* Loeb, Pfluger's Archiv, Vol. 88, p. 68, 1901. Am. Jour. Physiology, Vol. 3, p. 327,
1900; Vol. 6, p. 411, 1902. Loeb und Gies, Pfluger's Archiv, Vol. 93, p. 246, 1902. Loeb,
Pfluger's Archiv, Vol. 107, p. 252, 1905.
48 DYNAMICS OF LIVING MATTER
While a small quantity of a salt with a bivalent metal thus suffices
to render a solution of a salt with a univalent cation harmless, it was
found that it was not possible to produce similar antitoxic effects through
the addition of a salt with an anion of higher valency. If sodium sulphate,
yyi
sodium citrate, etc., was added to a — NaCl solution, the latter continued
2
to remain toxic for the Fundulus egg.
It is remarkable that not only the solutions of a salt with a univalent
cation, like NaCl, can be rendered harmless by a salt with a bivalent
cation, e.g. ZnS04, but that also the reverse is true; namely, that a
toxic solution of ZnS04 can be rendered harmless by a solution of
NaCl, provided the concentration of the ZnS04 is not too high. In
ioo c.c. of a § m NaCl solution no Fundulus egg forms an embryo.
When from 2 to 8 c.c. — solution of ZnSO. are added to this NaCl
64
solution, just as many eggs form embryos as in sea water or distilled
w
water. If, however, from 4 to 8 c.c. of a — ZnSO. solution are added
64 4
to 100 c.c. distilled water, not a single egg is able to form an embryo,
although in pure distilled water these eggs live and develop as well as
in sea water. The Zn-ions are therefore not only able to prevent the
toxic effects of a pure NaCl solution, but the NaCl of this solution also
prevents, in this case, the toxic effects of the Zn-ions.
The quantitative relations are of some interest. About 4 c.c. —
64
solution of a salt with a bivalent metal are required to render 100 c.c.
of a § m NaCl solution harmless. We may therefore say that for this
concentration of NaCl one ion of the bivalent metal suffices to render
1000 molecules of the salt with the univalent metal harmless. When a
/yyt
NaCl solution of a lower concentration, namely, f m or — is used,
less salt with a bivalent metal is required for the antitoxic effect than in
the case of a f m solution. If we use a NaCl solution with a concen-
tration of or below — , it is no longer harmful for the eggs of Fundulus.
4
If we use stronger solutions than f m, we soon reach a limit where the
addition of a salt with a bivalent metal no longer renders the solution
harmless. It is possible that, at this limit, the loss of water on the
part of the egg acts harmfully, and this effect, of course, cannot be
antagonized by the addition of another salt. If we try to determine
how much NaCl is needed in order to render a solution of ZnS04 harm-
less, we find that a comparatively large amount of NaCl is required for
GENERAL PHYSICAL CONSTITUTION OF LIVING MATTER 49
this purpose. In order to prevent the poisonous effect of a — ZnS04
solution, so much NaCl had to be added that the concentration of the
m
NaCl in the solution was about -=r. About ko molecules of NaCl were
8 J
therefore required to render one molecule of ZnS04 harmless. The fact
that the antitoxic effects of the salts with bivalent cations are so much
greater than those of the salts with univalent cations is possibly respon-
sible for the fact that I did not succeed in rendering a § m NaCl solution
harmless through the addition of a salt with a univalent cation. The
concentration of the solution would become so high that this might be
sufficient to kill the eggs. The salts of certain metals are especially
toxic, it being impossible to use those like Cu or Hg for antitoxic effects,
as they cause coagulation of the contents of the egg in smaller concen-
trations than are required for the antitoxic effects of such a solution.
The development of the egg of Fundulus requires at summer tem-
perature from about twelve to twenty-four days. If we use a Ca salt
to render a — or f m NaCl solution harmless, an embryo can be formed,
and it may hatch, but will then die; if, however, a Zn or Ba salt be used
for this purpose, an embryo is formed, and it may develop for a number
of days quite normally; but it dies before its development is complete.
If we allow the egg to complete its development in distilled water or
sea water, and put the larva, after it has hatched, into a mixture of
100 c.c. — NaCl, and a small amount of a Ba, or Co, or Zn salt, the
2
embryo dies even more quickly than if put into the pure NaCl solution.
These facts indicate that for this fish the ZnS04 remains toxic even
in the presence of the NaCl, and that these two salts are only antago-
nistic as long as the fish is surrounded by the egg membrane. This sug-
gests the idea that the antagonism between these two salts is due only to
the fact that they retard each other's rapidity of diffusion into the egg.*
If the egg is put immediately after fertilization into a — NaCl solution,
2
very soon so much NaCl diffuses into the egg that it poisons the fish.
The same is true if a small amount of ZnS04 is put into distilled water.
But if both salts are put together into the distilled water, neither the
NaCl nor the ZnS04 can diffuse as rapidly into the egg, and the germ
lives long enough to form an embryo. In a few days, however, death
occurs, showing that the diffusion of the ZnS04 was not prevented,
but only retarded. Another fact corroborates the idea that it is only
* Loeb, Pfluge^s Archiv, Vol. 107, p. 252, 1905.
50 DYNAMICS OF LIVING MATTER
the rate of diffusion of salts through the membrane which is retarded in
this case. A pure NaCl of the concentration — or f m only prevents
the formation of an embryo when the egg is put into the solution imme-
diately after fertilization. If, however, the egg is put for the first twenty-
four hours after fertilization into normal sea water and then into the pure
fyt
NaCl solution of the above-mentioned concentration, the — or # m
' 2 8
NaCl solution is not so toxic. In all probability the membrane of the
egg or the cells becomes more hardened or less permeable during the
first twenty-four hours.
The antagonistic effects between two salts with a bivalent cation
are not so general, yet I found that \ c.c. of a -fg m SrCL, solution
diminished somewhat the toxicity of a -^ m solution of MgCl2.
While in the case of the membrane of the newly laid Fundulus egg,
the addition of a trace of a salt with a bivalent cation sufficed to anni-
hilate or diminish the toxic effect of a pure NaCl solution, we never
find such simple relations for the Fundulus after it is hatched or for
any living cell that is exposed directly to the solution without the inter-
ference of a dead membrane, like the one which surrounds the fish egg.
For such directly exposed living tissues or animals, it is a rule that a
pure NaCl solution of sufficient concentration requires, besides the
CaCl2, a trace of KC1, in order to become harmless, as was shown in the
above-mentioned case of marine Gammarus. Besides, it is not possible
to substitute in that case for the Ca any bivalent cation; only Sr can
serve as a substitute for Ca in these cases. These limitations become
intelligible on the assumption that the surrounding salts diffuse slowly
into the cells. As long as this diffusion is so slow that the secretory
activity of the cells or glands of an animal may remove them as fast as
they enter, the cell or the animal may live in such a solution. I consider
fit
this the reason why a Fundulus may live in a — NaCl solution, while it
o
cannot live in a — NaCl solution. A second condition for the main-
2
tenance of life is, according to this hypothesis, the continuation of the
action of the secretory mechanism. If the latter depends on the con-
tractile power of the protoplasm, as I believe it does, we can understand
that, in order to make a NaCl solution harmless, not only Ca but also
K are required. We shall see in a later lecture that apparently Na,
Ca, and K are required for the contractile phenomena of protoplasm.
Hober and Gordon* have pointed out the existence of an antago-
* Hober und Gordon, Hofmeister 's Beitrage zur chtmischen Physiologic und Pathologie,
Vol. 5, p. 432, 1904.
GENERAL PHYSICAL CONSTITUTION OF LIVING MATTER 51
nism between the precipitating effects of salts of univalent and bivalent
metals, which Linder and Picton had already found. If arsenic sulphide
is precipitated with a mixture of two salts with a univalent cation, or
of two salts with a bivalent cation, the effects of the two salts are added
to each other. If a mixture of a salt with a univalent cation and a salt
with a bivalent cation is used, however, for the precipitation, the result
is an inhibition instead of a summation of the effects. Hober and
Gordon have repeated and confirmed this observation. In addition, they
•have found that, just as in my own experiments, the valency of the
anion plays no role. I am not able to state whether this explains the
observations made on Fundulus.
It is rather remarkable that many authors have found distilled water
to be poisonous for fresh-water animals. Locke showed that some
authors had been deceived by the fact that their distilled water contained
traces of copper salts, owing to the fact that the water had been distilled
in copper vessels. But Bullot* found that for fresh-water Gammarus
distilled water is toxic even if distilled with all necessary precautions in
Jena glass or quartz or platinum vessels, and if care is taken that it is
free from ammonia. He found that if a trace of NaCl is added to the
distilled water (so that the concentration of the latter was 0.00008 N)
fresh-water Gammarus could live indefinitely in the distilled water.
The presence of a trace of NaCl in the distilled water possibly preserves
the membrane better, or maintains better the secretory activity of the
cells so that the animal can be freed from the excess of water which
diffuses into it.
Dr. Wolfgang Ostwaldf investigated the duration of life of the same
fresh-water Gammarus in solutions of higher concentration. He
found that these animals live longer in a mixture of one hundred mole-
cules NaCl, two molecules KC1, and two molecules CaCL,, than in a
pure sugar or NaCl solution of the same concentration. This is in
harmony with the assumption that the absorption as well as the secretive
action of the cells requires the presence of Na, Ca, and K in definite
proportions, as we shall see more fully later.
In connection with these experiments I made an observation which
possibly may become of some use in the study of the phenomena of adap-
tation. When marine Gammarus is put into sea water, which has been
diluted with various quantities of distilled water, one notices that, with
increasing dilution of the sea water, the duration of life of the Gammarus
at first diminishes but little ; that, however, at a certain degree of dilu-
tion (about ten times that of the normal sea water) the duration of life
* Bullot, University of California Publications, Physiology, Vol. 1, p. 199, 1904.
t W. Ostwald, Pfluger's Archiv, Vol. 106, p. 568, 1905.
52 DYNAMICS OF LIVING MATTER
decreases quite suddenly. It is obvious that the discontinuity in the
curve of duration of life means that here a new condition, or a group
of new conditions, enters which before that time were not noticeable.
What are these conditions? Experiments which I have recently made
on the eggs of sea urchins showed that up to a certain degree the
dilution of the sea water with fresh water killed the eggs only slowly,
but that beyond a certain degree of dilution death was rather sudden.
This sudden death was due to a process of cytolysis in which the eggs
were transformed into "shadows." I am inclined to believe that some-
thing similar occurs in certain cells of marine Gammarus and of marine
animals in general, when the dilution of the sea water falls below a
certain limit.
This idea receives some support from the fact that Wolfgang Ostwald
found that a rise in the concentration of the sea water above a certain
limit also caused a sudden decline in the vitality curve of fresh-water
Gammarus. If the concentration of the sea water be raised above a
certain point, the eggs of the sea urchin also undergo cytolysis.*
* Loeb, Pflugcr's Archiv, Vol. 103, p. 257, 1904.
LECTURE IV
ON SOME PHYSICAL MANIFESTATIONS OF LIFE
i. Hypotheses of Muscular Contraction
The phenomena which allow us to discriminate between dead and
living matter are physical processes, e.g. in higher animals, the contraction
of the heart, the respiratory and other muscular motions. If the chemi-
cal processes in living matter and the physical changes they bring about
in the colloids were entirely known, the physical manifestations of life
would also be clear to us. The periodic character of many of the mani-
festations of life suggests the idea that these processes occur in several
phases which are probably connected, partially at least, in a catenary
way, so that the preceding process has effects which cause the subse-
quent phase of the process.
These catenary mechanisms are for the most part still unknown.
Inasmuch as the number of possible changes in the condition of colloids
seems limited, the impression might be gathered that by a guess the
whole secret of the physical manifestations of life might be unraveled.
Such surmises find their way occasionally into print. As a rule, those
who are familiar with the specific case for which the guess is made are
not helped by it. It is not worth while to devote any time to the point-
ing out of the futility if not open absurdity of most of these attempts.
The origin of animal heat from chemical energy offers no further
mystery. We know that a kilo of sugar yields about four thousand
calories of heat, if burned in the laboratory, and that it gives the same
heat if oxidized in the body. In our modern theory of nutrition, the
heat value of the various kinds of food is justly used as the basis for
the calculation of their nutritive value. The times are gone when physi-
cians and biologists dared to raise the objection — as they did against
Robert Mayer — that our body inherits its heat.
As far as the transformation of chemical energy into mechanical
energy in the muscle is concerned, Robert Mayer and Helmholtz con-
sidered the muscle as a thermodynamical machine. They assumed
that in the muscle the heat produced by chemical processes is partly
S3
54 DYNAMICS OF LIVING MATTER
transformed into mechanical energy; but they refrained from stating
how this transformation occurs. Engelmann tried to fill this gap.*
Striped muscle consists of alternating stripes of optically isotropic and
anisotropic substance. Engelmann observed that in the contraction
of the muscle the anisotropic substance increases in volume, while the
isotropic substance decreases. As the total volume of the muscle does
not change during the contraction, Engelmann concluded that part
of the liquid of the isotropic substance diffused into the anisotropic
during contraction. He showed by experiments on violin strings
(made of catgut) that such a process of absorption can be produced by
heat. The violin strings show the same double refraction as the aniso-
tropic stripes in the muscle. When a violin string is suspended in
water, and the latter suddenly heated, the string contracts, and is able
to lift a weight in this contraction. This shortening of the string is
caused by an absorption of water by the string; and this imbibition is
caused by the increase in temperature. Like the contracting muscle,
the violin string, in this case, becomes shorter and thicker. The process
is reversible as the string elongates again upon cooling.
In the case of the muscle, Engelmann assumes that through the
stimulus which causes muscular contraction, heat is produced (through
the oxidation of carbohydrates) ; and that the increase in temperature
causes the anisotropic substance to absorb water from the isotropic
substance. This causes the change of form in the muscle — the thicken-
ing and shortening — by which it is able to lift a weight.
For such a shortening of the violin string through heating, an increase
of about io° in the temperature of the water is necessary, while
the temperature of a frog's muscle during a single contraction increases
only by 0.0010. Engelmann points out, however, that the increase in
the temperature of the whole muscle does not indicate the rise in tem-
perature in individual spots in the muscle, which may be considerably
higher. The foci of combustion heat the whole mass of the muscle,
and we measure only the latter increase of temperature, which may
of course be quite small. Provided we grant this, it is necessary to
assume that the heat is sufficiently rapidly dissipated by conduction to
allow the rapid succession of relaxation and contraction of the muscle
in tetanus. We know that the muscles can contract and relax many
times a second, e.g. the muscles of the wings of insects contract and
relax more than a hundred times a second. I do not believe that the
process of dissipation of heat in liquids is rapid enough to make Engel-
mann's hypothesis probable, or even possible. It is, however, conceiv-
able that with a slight modification his hypothesis may be rendered free
* Engelmann, Ueber den Ur sprung der Muskelkraft, Leipzig, 1893.
ON SOME PHYSICAL MANIFESTATIONS OF LIFE 55
from objections such as we have mentioned ; namely, by assuming
that chemical, not thermal conditions determine the absorbtion of fluid
by the anisotropic substance. The action of the nerve upon the muscle
might consist in facilitating a chemical change which increases the
absorption of water by the anisotropic substance of the muscle.
2. Quincke's Theory of Protoplasmic Motion
The thermodynamic conception of muscular contraction has been
abandoned by many authors, and the surface energy has been con-
sidered in its stead as the cause of muscular contraction and work.
D'Arsonval, Imbert, and more recently Bernstein, have tried to offer a
hypothesis of this kind. We shall understand these hypotheses better
if we first consider Quincke's theory of protoplasmic motion.*
When a drop of oil is put on the surface of water which is in contact
with air, the oil spreads in an extremely thin layer at the limit between
water and air. This process continues until a film of oil exists between
water and air. The conditions for the spreading of the oil on the sur-
face of the water are as follows:
the particle of oil O at the left end
of the oil drop (Fig. 7) is under the
influence of three surface tensions
which pull at it in three different - vj-zt^I"""" water
directions, OA, OB, and OC, and
with different force. One is the
surface tension between air and water, which tends to pull the
particle from O in the direction OA. The second is the surface
tension OB at the limit of oil and air, which tends to pull the
particle O in the direction of the tangent OB from O. The third
force is the surface tension at the limit of oil and water, which tends
to pull the particle in the direction of the tangent OC from O. The
surface tension at the limit of water and air is greater than the sum of
the surface tensions at the limit between oil and air, and oil and water.
The surface tension between air and water is 8.25 mg., between oil and
air 3.76 mg., and between oil and water 2.73 mg. The particle O will
therefore be pulled toward the left ; and the same will happen with the
next particle of oil, until the surface water air is substituted by the
surface oil air.
These phenomena of spreading are accompanied by motions in the
neighboring particles of liquid. If oil spreads at the surface of water,
* Quincke, Sitzungsberichte der Berliner Akademie der Wissensch., p. 791, 18S8.
56 DYNAMICS OF LIVING MATTER
the moving oil will, through friction, set the adjoining particles of water
also in motion. The superficial layers of water, therefore, will move
away from the center of spreading, and water will move toward the
center from the interior, and
from below. The arrows in
Fig. 8 represent the currents
in the water caused by the
spreading of the oil.
Quincke holds that such
WATER ^
FlG g phenomena of spreading are
the cause of all protoplasmic
streaming. Such a streaming occurs constantly in the cells of Chara
or Nitella. Quincke gives the following explanation for this process :
all protoplasm contains oil or fat, and the surface layer of each cell
must, therefore, be surrounded by a film of oil or fat. The oil will
form through hydrolysis traces of fatty acid. The protoplasm contains
substances which form soaps with the fatty acid. A soap solution
must spread at the limit between oil and water, as the surface tension
between oil and water is greater than the sums of surface tension
between oil and soap solution, and between water and soap solution
(which is zero). When the soap solution spreads, it must pull with it
the adjacent particles of protoplasm. In this phenomenon of spreading,
new particles of the surface of oil come in contact with protoplasm,
new soap is formed, and the process is repeated. These phenomena
of spreading, which constantly repeat themselves, furnish the energy
for the constant streaming of protoplasm. The protoplasmic streaming
occurs in the case of Chara or Nitella in one direction only. Quincke
believes that this is due to an asymmetry in the structure of the cell,
which renders the resistance to the streaming greater in one direction
than in the opposite direction. Hence, the streaming occurs in one
direction only; namely, that of least resistance.
The motion of an Amoeba can be imitated by bringing a drop of
olive oil which contains a trace of fatty acid upon a one half to two
per cent solution of Na2C03. The oil, in this case, forms at its surface a
film of solid soap. As soon as this dissolves at one spot, soap solution
must spread at the surface of water and oil, and the moving soap solution
must set also the neighboring layer of oil into motion. In the oil drop,
therefore, two movements must occur, one at the periphery, which is
directed away from, and one in the center, which is directed toward,
the center of spreading. The arrows in Fig. 9 indicate these streams.
The particles that flow from the interior toward the periphery produce
a bulging out, and this is the analogue of the formation of a pseudo-
ON SOME PHYSICAL MANIFESTATIONS OF LIFE 57
podium. According to Berthold,* the phenomena of streaming in
the interior of an Amoeba in the process of the formation of a pseudo-
podium are such as to agree with the ideas of Quincke. Butschli
has come to the same conclusion. It
seems to me, however, that if it is s "^ «~ '*- "^
true that the Amoeba is covered with "7 v, l ( ( C *?
a solid surface film, one condition for 1 I ^^>^^=r -^T^c-^
the formation of a pseudopodium must _^?j^ r^% \ V\% V v\
be a local liquefaction of protoplasm. SlU \ ^-jO JSs J J \
In consequence of such a liquefaction, soAPl V-^^r^-^^ *" * I
new protoplasm must flow out, which, "X\f f *- ~~^ ^ *"" /
subsequently, will form a new solid ^\ ^ ^M v /
film at its surface. This may again **~* Nk -^ -* >* / J /
be liquefied, and a new streaming may { /^^^—^^^
occur, etc. Such liquefactions can be > * \ f ^ ^ ^ <^
caused by lack of oxygen, as we saw *- ^ *^_ ^
in a previous lecture; but they may fig. 9.- after butschli.
also be caused by other chemical
changes. I am inclined to believe that phenomena of liquefaction play
at least some role in these processes of protoplasmic motion.
Imbertf published several years ago a hypothesis concerning the
contraction of smooth muscle fibers, which assumes that the "stimulus"
which causes the contraction of smooth muscles produces an increase
in the surface tension between the longitudinal fibrils and the surround-
ing liquid of the muscle cell. These fibrils are long and thin cylinders;
every increase in surface tension must have a tendency to make these
fibrils more spherical, i.e. thicker and shorter. Such a change of form
occurs indeed during contraction, but it is difficult to understand why
the fibrils do not assume this form under the influence of surface tension
alone, without stimulation. To meet this difficulty, Imbert assumes
that smooth muscle fibers cannot contract unless they are stretched
passively. He presupposes that their arrangement in the body is such
that this prerequisite is generally fulfilled.
Bernstein has tried to explain away some of the weak spots in this
hypothesis. J The surface energy at the limit between two media is
equal to the product of surface tension into the surface. The work
which surface tension can do is measured by the product of the decrease
in surface, times the surface tension. From this it follows that the sur-
face energy can do considerable work only, when the decrease in surface
* Berthold, Studien uber die Protoplas?namechanik, Leipzig, 18S6.
t Imbert, Archives de physiol., 5th series, Vol. 9, p. 289, 1897.
% Bernstein, PflUger's Archiv, Vol. 85, p. 271, 1901.
5 8 DYNAMICS OF LIVING MATTER
is large. From this Bernstein justly argues that Imbert's assumption
is incorrect, inasmuch as the area required for the work the muscle
really does, must be much larger than that between the fibrils and the
neighboring liquid. Bernstein therefore assumes that the fibril consists
of a row of quite small ellipsoids, whose long axis is in the direction of
the fibrils, and whose form is determined by elastic forces. An increase
in the surface tension must make these ellipsoid elements more spherical,
and thus the fibril becomes shorter and thicker.
How can the nerve impulse or an artificial stimulation of the muscle
increase the surface tension? There are several possibilities. Sub-
stances might be formed in this case which increase the surface tension
at the limit between Bernstein's hypothetical ellipsoids and the surround-
ing liquid. Another possibility might be that, through the process of
innervation or stimulation, an existing difference of electrical potential
between the ellipsoids and the surrounding liquid might be diminished.
D'Arsonval explains the efficiency of electrical stimuli in this way *
Hermann has offered another hypothesis ; namely, that the contrac-
tion is a process of coagulation, and the relaxation, a process of lique-
faction.! He was led to this idea by the fact that the change in form
which the muscle undergoes in the case of rigor mortis is similar to
that in contraction, and that moreover a number of other features are
common to both. Although all these hypotheses concerning muscular
contraction have been known for a number of years, none has led to a
new discovery. The reason lies possibly in the fact ,that one or more
links in the catenary series of processes which underlie muscular con-
traction have been ignored in these hypotheses. It is well known that
a muscle gains in mass through contractions, and that it undergoes
atrophy when it remains at rest. This fact indicates, in my opinion,
very clearly that phenomena or reactions which directly or indirectly
lead to growth form a part in the process of muscular contraction.
I consider it quite possible that no hypothesis concerning muscular
contraction will prove fertile until this relation between activity and
growth of the muscle is recognized.
3. Concerning the Theory of Cell Division
Were scientists with a purely physical training to be asked to give a
hypothesis concerning cell division, I believe that their hypothesis would
not take into consideration the phenomena of growth. Nevertheless,
these phenomena form an obvious link in the catenary series of processes
* D'Arsonval, Archives de physiol., 5th series, Vol. I, p. 460, 1889.
t Hermann, Handbuch der Physiologie, Vol. 1, Part I, p. 332.
ON SOME PHYSICAL MANIFESTATIONS OF LIFE 59
which result in the division of the nucleus and the cell. It had been
tacitly recognized by botanists that the growth of a cell precedes its
division and is possibly the cause of the division. The botanist J. Sachs
was the first to definitely state that in each species the ultimate size of
a cell is a constant for each organ, and that two individuals of the same
species but of different size differ in regard to the number, but not in
regard to the size of their cells.* Amelung, a pupil of Sachs, determined
the correctness of Sachs's theory by actual counts. Sachs, in addition,
recognized that wherever there were large masses of protoplasm, e.g.
in Siphoneae and other cceloblasts, many nuclei were scattered throughout
the protoplasm. He inferred from this that "each nucleus is only
able to gather around itself and control a limited mass of protoplasm." f
He points out that in the case of the animal egg the reserve material
— fat granules, proteins, and carbohydrates — are partly transformed
into the chromatin substances of the nuclei, and that the cell division
of the egg results in the cells reaching that final size in which each
nucleus has gathered around itself that mass of protoplasm which it is
able to control. Morgan % and Driesch§ tested and confirmed the idea
of Sachs for the eggs of Echinoderms. Driesch produced artificially
larvae of sea urchins of one eighth, one fourth, and one half their normal
size by isolating a single cleavage cell in one of the first stages of seg-
mentation of the fertilized sea-urchin egg. He counted in each of the
dwarf gastrulae resulting from these partial eggs the number of mesen-
chyme cells and found that the larvae from a \ blastomere possessed
only |-, those from a \ blastomere only \, and those from a \ blasto-
mere only \ of the number of cells which a normal larva developing
from a whole egg possessed. Moreover, he could show that when two
eggs were caused to fuse so as to produce a single larva of double
size, the gastrulae of such larvae had twice the number of mesenchyme
cells. Driesch drew from his observations the conclusion that each
morphogenetic process in an egg reaches its natural end when the cells
formed in the process have reached their final size.
Gerassimowll found that by exposing dividing cells of Spirogyra
to a low temperature the division became irregular, and it happened
that the nuclear material instead of being divided between the two
* J. v. Sachs, " Physiologische Notizen," VI, Flora, 1893.
t Sachs, " Phvsiologische Notizen," IX, p. 425, Flora, 1895.
j Morgan, " Studies of the ' Partial ' Larvae of Sphserechinus," Arch, fur Entwickeluttgs-
mechanik, Vol. II, 1895. "The Proportionate Development of Partial Embryos," ibid.,
Vol. XIII, 1901. "The Gastrulation of the Partial Embryos of Sphsrechinus," ibid., Vol.
XVI, 1903.
§ Driesch, "Von der Beendigung morphogener Elementarprocesse," Arch, fur Enhvicke-
lungsmechanik, Vol. VI, 1898. "Die isolirten Blastomeren des Echinidenkeims," ibid., Vol.
X, 1900.
|| Gerassimow, Zeitsch.fur allgemeine Physiologie, Vol. 1, p. 220, 1902.
60 DYNAMICS OF LIVING MATTER
masses of protoplasm remained in one of the two daughter cells ; some-
times all the chromosomes were united into one nucleus and sometimes
he obtained two nuclei. He found that cells with an increased mass of
chromatin only began to divide after their protoplasm had reached
a much greater mass than that found in the normal cells with half
the mass of the chromosomes. This fact seems to indicate that cell
division is determined by the ratio of the mass of the chromosomes
to that of the protoplasm. If the mass of the chromosomes in a cell
is increased, the tendency for cell division does not develop until the
mass of protoplasm is increased also. It is the merit of Boveri to have
found the law which governs this condition for cell division.* He
compared the process of segmentation in normally fertilized fragments
of sea-urchin eggs, which contained the normal number of chromo-
somes, with that of enucleated fragments which contained only the
sperm nucleus, and whose mass of chromatin was only one half of
that of the normal fertilized egg. In order to understand his results,
the reader's attention should be called to the following fact: in the
process of cell division each daughter nucleus of the egg contains just
as many chromosomes as the mother nucleus, but the mass of chromatin
(and possibly the other constituents of the nucleus) of each chromosome
in the daughter nucleus is only one half of that of the corresponding
chromosome of the mother nucleus. The next phase — the resting stage
between two divisions — consists in the growth of the chromosomes
of the two daughter nuclei until they have reached the mass of
the original chromosomes and then a new nuclear and cell division
begins. The material for the growth of the chromosomes is furnished
by the protoplasm and according to the above-quoted idea of Sachs
by the reserve material included in the protoplasm and not by the
"living" part of the latter itself. It is, however, questionable whether
this latter discrimination has any real basis. In this way the process
of cell division in the egg consists in the gradual transformation of proto-
plasmic into chromatin material of the nucleus until a definite ratio
between the mass of the chromosomes and the protoplasm is reached.
When this is established, no new cell divisions are possible until the
mass of the protoplasm is increased again through the absorption of
food stuffs on the part of the cell. The process of the transformation
of protoplasm into chromatin is necessarily rendered discontinuous
through the fact that the chromosomes cannot grow indefinitely, but
that growth will stop as soon as they have reached a certain size,
and this fact leads apparently to the process of nuclear divisions. I
* Boveri, Zellen-Studien, Heft 5. Ueber die Abhangigkeit der Kerngrosse und Zellen-
zahl der Seeigel-Larven von der Chromosomenzahl der Ausgangszellen, Jena, 1905.
ON SOME PHYSICAL MANIFESTATIONS OF LIFE 6 1
have thought of the possibility that the continuation of the synthetical
process which leads to the formation of nuclear material from certain
constituents of the protoplasm gives rise to the formation of astrospheres
as soon as the maximal growth of the chromosomes is reached. But
this does not need to enter into our consideration for the present.
Since each daughter nucleus of a dividing blastomere has the same
number of chromosomes as the original nucleus of the egg, it is clear
that in a normally fertilized egg each nucleus has twice the mass of
chromosomes as the nucleus of a merogonic egg, i.e. an enucleated frag-
ment of protoplasm which has only the sperm nucleus. Boveri has
not only ascertained this fact but he has also ascertained the further fact
that the final size of the cells after the cell divisions have come to a
standstill is always in proportion to the original mass of the chromatin
contained in the egg ; the cells of the merogonic embryo, e.g. the mesen-
chyme cells, are only half the size of the same cells in the normally
fertilized embryo. Driesch has just furnished a further proof of Boveri's
law, that the final ratio of the mass of the chromatin substance in a
nucleus to the mass of protoplasm is a constant in a given species.
He compared the size of the mesenchyme cells in a sea-urchin embryo
produced by artificial parthenogenesis with those of a normally fertilized
egg and found them half of the size of the latter. When the fertilized
eggs and the parthenogenetic eggs are equal in size from the start, —
which is practically the case if eggs of the same female are used, — the
process of the formation of mesenchyme cells comes to a standstill in
the normally fertilized eggs when the number of mesenchyme cells is
half as large as the final number of mesenchyme cells found in the
parthenogenetic egg.* As a matter of fact, Boveri's results as well as
those of Driesch were obtained by counting the cells formed by eggs
of equal size and not by only measuring the size of the cells. It is
most remarkable that certain apparent exceptions to Boveri's law
which Driesch has actually found have been predicted by Boveri.
The fact that the process of cell division comes to a standstill when
the ratio of the mass of the chromosomes in the nuclei of an egg or an
organ to that of the surrounding protoplasm reaches a certain limit,
suggests in my opinion the possibility that this ratio is determined by
the laws of mass action and chemical equilibrium. If this is correct,
the synthesis of nuclein compounds from the protoplasmic constituents
must be a reversible process. This suggestion would gain in probability
if it could be shown that a reduction of size in protoplasm in the case of
starvation is also followed or accompanied by a reduction in the size
of the nuclei.
* Driesch, Archiv fur Entzvickelungsmechanik, Vol. 19, p. 648, 1905.
62 DYNAMICS OF LIVING MATTER
The fact that the cell division is as a rule preceded by a synthetical
process explains possibly the fact mentioned in the second lecture that
the phenomena of cell division in a fertilized egg come soon if not
immediately to a standstill when the atmospheric oxygen is with-
drawn from the egg. We have mentioned Schmiedeberg's view in
regard to the role of oxygen in synthetical processes. But even if this
view were not correct, we can understand that lack of oxygen might
indirectly interfere with the synthesis of the nuclein compounds.
E. P. Lyon has shown that the chemical conditions and processes
in the cell differ in the various phases of cell division. He found that
during different stages of cell division the egg of the sea urchin shows
a different resistance to the effects of HCN, and this difference repeats
itself during each of the successive segmentations. More recently he
has added the important fact that the production of C02 on the part
of the egg of the sea urchin also undergoes periodic variations during
segmentation.
If we now turn to the physical side of the phenomena of cell division,
we shall meet almost the same uncertainty which confronted us in the
case of muscular contraction. We shall therefore confine ourselves to
the enumeration of a few facts, with occasional hints for possible
further work.
When we watch the process of cell division in an egg, we can dis-
criminate at least three distinct phases of this process : first, the ap-
pearance of systems of radiation — the so-called astrospheres — in the
protoplasm of the cell. The second phase is the disappearance (liquefac-
tion?) of the nuclear wall, and the division and migration of certain
constituents of the nucleus, namely, the chromosomes toward the centers
of the astrospheres, and the formation of two new nuclei. The third
phase consists in the separation of the protoplasm into two pieces in
a plane, which, from the position of the astrospheres, as a rule, can be
predicted. This latter separation is the process of cell division proper.
If newly fertilized eggs of the sea urchin are put into sea water,
whose osmotic pressure has been adequately raised by the addition of
some salt, e.g. NaCl, or sugar, no segmentation occurs as long as the
eggs remain in this solution. If they are brought back from this solu-
tion into normal sea water, they will segment, provided they have not
been left too many hours in the hypertonic sea water. There is, how-
ever, a characteristic difference between this segmentation and the
normal segmentation. If the eggs are brought back into normal sea
water after two hours, they do not divide, as a rule, first into two, and
then into four cells, but into three or four cells simultaneously. If they
are left for three or four hours in the hypertonic solution, and then
ON SOME PHYSICAL MANIFESTATIONS OF LIFE 63
brought back into normal sea water, they break apart into from six
to sixteen cells simultaneously in about ten or twenty minutes after being
put back into normal sea water. If they remain for five or six hours
in the hypertonic solution, many eggs suffer. If they do not suffer
they soon break up, when put into normal sea water, into a still larger
number of cells than if they remained only for three or four hours in
the hypertonic sea water. I have seen such eggs divide simultaneously
into about forty cells, or more, in from ten to twenty minutes after
being put back into normal sea water. These phenomena of segmen-
tation are accompanied by violent phenomena of streaming or proto-
plasmic motion at the surface of the egg. From these facts I concluded
that while the hypertonic sea water inhibits the cell division, it allows
the division of the nucleus, which precedes the segmentation of the
protoplasm.* W. W. Normanf undertook a histological examination
of the eggs under these conditions. He found that if the concentra-
tion of the sea water be adequately, but not excessively, raised through
the addition of a definite amount of NaCl, KC1, or MgCl2, the nuclei
of the eggs divide in the hypertonic sea water karyokinetically, into
two, four, and eight successively, while no cell division occurs. When
such an egg with eight nuclei is put back into normal sea water,
it divides as a rule into more than eight cells simultaneously. If a
slightly too high concentration is used, the distribution of the nuclei
in the egg does not become so regular; if the concentration is still a
little higher, an excessive number of astrospheres is formed, as Morgan
and Norman found. In this case, the nuclear material is often not
scattered in the egg, although the nucleus seems to be broken into smaller
fragments, for if brought back into normal sea water such eggs break
up rapidly into a larger number of cells. R. Hertwig had already
observed the formation of astrospheres in the unfertilized eggs of the
sea urchin when he added a little sulphate of quinine to the sea water,
and Morgan applied the method used by myself and Norman to the
unfertilized egg and found an excessive number of astrospheres, just
as Norman had observed in the fertilized egg. J
It is obvious from these and other experiments not mentioned here
that the loss of water on the part of the fertilized egg ultimately retards all
the phases of nuclear and cell division, but not all quantitatively alike.
It seems that the chemical process of transformation of protoplasmic into
chromatin material is less interfered with than the cell division proper.
This follows from the fact that the chromosomes may divide without
* Loeb, Jour, of Morphology, Vol. 7, p. 253, 1892.
t W. W. Norman, Archiv fur Entwickelungsmechanik, Vol. 3, p. 106, 1896.
% Morgan, Archiv fur Entivickelungsmechanik, Vol. 8, p. 448, 1899.
64 DYNAMICS OF LIVING MATTER
cell division. Under normal conditions, the growth of the chromo
somes is followed by a formation of astrospheres and division of the
nuclei, and this in turn is followed by a cell division. The loss of water
which the egg undergoes in the hypertonic sea water seems to inter-
fere mostly with the cell division. It is possible that the viscosity of
the protoplasm is increased by the loss of water, and that this condi-
tion interferes somewhat with the migration of chromosomes after they
have divided and still more with the segmentation of the protoplasm.
The growth of the chromosomes and the subsequent formation of as-
trospheres seem, however, to continue for some time in the hypertonic
sea water.
O. and R. Hertwig (as well as Roux) have noticed that as a rule
the plane of division of a non-spherical cell is at right angles with the
direction of the greatest diameter, or extension of the cell. Driesch
has given a nice experimental proof for this rule. If the newly fer-
tilized egg of the sea urchin be gently pressed under a cover glass, so
that it is slightly flattened, the plane of division is at right angles to the
slide. The position of the plane of cleavage is determined by the
position of the nuclear spindle, and the latter depends upon the position
of the centrosomes or astrospheres. The question hence arises, How
does it happen that in most cases the common diameter of the two
astrospheres coincides with the longest diameter of a cell ? This posi-
tion of the astrospheres or centrosomes becomes comprehensible on the
assumption that these organs not only repel each other, but are also
repelled by the external surface of the nuclei and the inner surface of
the cell limit. The forces involved in this repulsion must be forces
such as occur in liquids, as the contents of the egg of the sea urchin
is mainly liquid. It must, moreover, be taken into consideration that
the space in which the process of cell division occurs, is generally of
microscopic and always of capillary dimensions. It is therefore quite
possible that the repelling forces in this case are capillary forces. There
is, however, another fact to be considered ; namely, that in the process
of cell division the egg of some animals becomes elliptic, with its long
axis falling in the direction of the common diameter of 'both astro-
spheres. This has given rise to the idea that the spindle or the astro-
spheres elongated the egg. I have often noticed — as others have
undoubtedly done before me — an elongation of the egg of the sea
urchin in the direction of the spindle, but this always occurred imme-
diately before the cell division. It gives easily the impression as if
contractile forces were active in radial directions in the astrospheres
and that these forces had something to do with the process of cell divi-
sion. Certain deviations from Hertwig's law may be only apparent.
ON SOME PHYSICAL MANIFESTATIONS OF LIFE 6$
Such exceptions occur in epithelial cells, but it is quite possible, that
not the whole cell but only one part of it is in this case the seat of the
processes which cause the orientation of the astrospheres or the cen-
trosomes.
R. Lillie has expressed the idea that electrical forces play a role
here. Were this idea correct, it should be an easy matter to control
the orientation of the plane of cleavage in the cell by means of a gal-
vanic current; such is, however, not the case, at least as far as our
present experience goes. If hydrodynamic and "contractile" forces are
responsible for the orientation of the astrospheres or centrosomes in the
cell, it should be expected that these latter organs are solid or at least
more viscous than the rest of the liquids of the cell. If the centro-
somes are fixed organs of the cells, and multiply by division, they must
naturally be solid or at least possess a solid surface. Alfred Fischer
assumed that the formation of astrospheres depended upon a process
of coagulation. This has not yet been proved, although this author has
imitated the well-known figures of astrospheres in coagulated proteins.
If the process of nuclear division in transparent cells, e.g. egg cells,
is observed, the impression is easily gathered that the astrospheres
cause a liquefaction of the nuclear membrane and an emulsification
of certain constituents of the nucleus. If this observation be correct,
the phenomena of spreading and the phenomena of streaming con-
nected with such a process might be the forces which carry the chro-
mosomes of the nucleus toward the center of the astrospheres. This
assumption is in harmony with the fact that the withdrawal of water
from the egg cell diminishes the velocity of the nuclear division,* inas-
much as the loss of water may easily increase the viscosity of protoplasm,
and thus diminish the velocity of the process of streaming, finally ren-
dering it entirely impossible.
The phenomena of streaming can be demonstrated most beauti-
fully in the experiment described above in which eggs of the sea urchin
were put into hypertonic sea water, whose concentration was just
adequate to prevent the cell division, without preventing the nuclear
division. When such eggs are put back into normal sea water after
about three hours, the most powerful phenomena of streaming may
be witnessed, resulting in the formation of knobs. The streaming
seems to occur around the chromosomes or fragments of nuclear mate-
rial as a center. Afterwards, each such knob, or projection, formed
by the streaming becomes a separate cell.f
* Loeb, Am. Jour, of Morphology, Vol. 7, p. 253, 1892.
t This amceboid, character of cell division had been observed and described before by
O. and R. Hertwig and called " KnospenfurchungP
66 DYNAMICS OF LIVING MATTER
In my earlier experiments on artificial parthenogenesis, I frequently
had opportunity to observe cell divisions of a character which made
it clear that phenomena of streaming underlie cell division, at least,
in these cases. Figures 10-13 give an illustration of such a case. The
egg had been treated with hypertonic sea water, and when put back
Fig. 10. Fig. ii. Fig. 12. Fig. 13.
into normal sea water divided as represented in these drawings. The
division began (as was frequently the case) on one side (Fig. 10), and
the protoplasm then flowed in the direction of the two arrows (Fig. 11)
in opposite directions toward the two nuclei. The connecting piece
becomes empty of protoplasm and only the pigmented solid surface
film is left (Fig. 12), and finally this also disappears (Fig. 13). It is,
however, possible that contractile forces acting in a radial direction
in an astrosphere might bring about similar results.
The process of the cell division proper seems to consist also of
several phases. A reduction of volume seems to occur in this process,
inasmuch as the combined volume of the two daughter cells appears
immediately after the division, smaller than the volume of the mother
cell. This diminution of volume may be due to a loss of water, or
watery liquid, on the part of the cell. There may also be a process of
gelation on the part of certain constituents of the cell, e.g. the nucleus,
which at this stage appears to form a solid mass, or possesses at its
surface a solid wall.
4. The Origin of Radiant Energy in Living Organisms
The first investigation of animal phosphorescence that was of any
consequence goes back to Faraday, who showed that the phosphores-
cent part of a glowworm continues to send out light if it be made into
a pulp. This observation speaks against the view of Kolliker and
Pfliiger that the phosphorescence of animals is a function of "living"
matter, and even, in certain cases, under the control of the nervous
system. They were led to their view by the observation that "stimu-
lation" could call forth the process of phosphorescence, while poisons
and high temperatures caused it to disappear. From this Pfliiger*
* Pfliiger 's Archiv, Vol. io, p. 251, 1875.
ON SOME PHYSICAL MANIFESTATIONS OF LIFE 6j
drew the conclusion that phosphorescent matter is irritable, and "irrita-
bility" is considered a sign of life. We must not, however, overlook
the possibility that stimulation of an animal may produce the process
of phosphorescence indirectly, e.g. by causing motions on the part of
the animal which bring the phosphorescent matter into contact with
oxygen. Giesebrecht * has furnished an absolute proof for the fact
that phosphorescence may be produced in animals by non-living mate-
rial. He found that certain pelagic copepods, e.g. Pleuromma gracile
and Leuckartia flaviensis show phosphorescence, and that this phe-
nomenon is confined to definite points of their body, which correspond
to the ducts of certain glands of the skin of the animals. These glands
secrete drops of a greenish yellow substance. As long as the animals
lie quiet there is no phosphorescence visible, but they show this phenom-
enon when pressed or heated, or if brought in contact with ammonia,
alcohol, or glycerine. This might easily be interpreted as signifying
that the phosphorescence of these animals is a phenomenon, which is
produced by the stimulation of the animal. Giesebrecht found, how-
ever, that the phosphorescence occurs only when the secretion of the
glands is brought to the surface of the animal, and comes in contact
with the sea water. He proved, moreover, that the secretion even re-
tains its power of phosphorescing after the death of the animal. Dead
copepods, which had been preserved in a dry condition for three weeks,
still showed the phosphorescence at the opening of the glands, whenever
they were put into water. The above-mentioned "stimuli" caused the
phosphorescence only indirectly, by causing the squeezing out of the
secretion of the glands from the duct.
How the contact of the secretion with water can cause the phos-
phorescence is not yet clear. Radziszewski f has found that a number
of organic compounds show phosphorescence at a comparatively low
temperature, e.g. io° C, when they come in contact with atmos-
pheric oxygen, and the reaction is alkaline. Among these substances
are the soaps of oleic acid, a number of alcohols, etc. This author
assumes that the phosphorescence of animals is caused in the same way.
Traces of the phosphorescent substances and of oxygen suffice for the
production of the phenomenon. We can readily understand that mo-
tions of an animal are favorable for the production of phosphorescence,
as they tend to bring the oxygen (e.g. in the tracheae of insects) in con-
tact with new particles of the phosphorescent substance. Giesebrecht
questions the importance of oxygen for this process, inasmuch as in
* Giesebrecht, Mittheilungen aus der zoologischen Station zu Neapel, Vol. 2, p. 648,
1895-
t Radziszewski, Liebig's Annalen der Chemie, 1880.
68 DYNAMICS OF LIVING MATTER
his experiments the animals also showed phosphorescence in boiled water;
but as very little oxygen suffices for the phenomenon, it is possible that
in Giesebrecht's experiments sufficient oxygen was present for the pro-
cess. The experimenters agree, in general, that free oxygen is neces-
sary for phosphorescence. It is possible, however, that the conditions
for phosphorescence may vary with the nature of the substance.
5. Electrical Phenomena in Living Organisms
When Galvani noticed that the muscles of the leg of a frog twitch
when touched with two metals, he believed that this phenomenon
indicated the production of electricity in living organisms. Volta
subsequently showed that the nerve-muscle preparation only acts as
a sensitive rheoscope. Thus a misunderstood biological observation
became the germ for the development of electrochemistry. It was
found afterward that living organisms produce indeed some electrical
energy, but in spite of the most diligent search nobody has yet been
able to prove that the electrical energy thus produced plays any role
in an essential life phenomenon, although this may be the case.
The liquids of the body must be the cause of the differences of
potential in the tissues as only the electrolytes dissolved in these liquids
are capable of producing differences of potential. The most common
instances of the production of a difference of electrical potential are
the cases of an active or
dying nerve or muscle. When
an element of a nerve is
active or injured, and one
electrode of a galvanometer
is applied to the active or
injured spot (Fig. 14), an-
other to the neighboring
Active or Resting or r
injured Normd resting, or normal element of
FlG. I4- the nerve or muscle, a cur-
rent of positive electricity
travels through the galvanometer from the resting, or normal, to the
active, or injured element of the nerve or muscle. The activity of
the muscle, or its injury, is accompanied by a production of acid,
i.e. carbonic, and possibly, lactic acid. According to Waller C02
is also produced in the active nerve.* I concluded from this that
these currents might be due to the formation of acid. The H-ions
have a much greater velocity of migration than any anion, and hence,
* Waller, Lectures on Physiology, I. On Animal Electricity, London, 1897.
f
+1
+
+
+
1 . -
+
+
+
ON SOME PHYSICAL MANIFESTATIONS OF LIFE 69
if in an active or injured element of the nerve or muscle acid is formed,
the hydrogen-ions must migrate faster into the neighboring tissue than
the anions. Consequently, the active element will have an excess of
free negatively charged ions, while the neighboring resting elements will
assume a positive charge (Fig. 14). I published this explanation of the
origin of currents of action in a preliminary way in an address at the
Naturalists' meeting in 1897.* Oker-Blom| has since expressed a
similar view in regard to the current of demarcation; and he mentions
that Tschagovetz has published a similar view in a Russian journal.
Ostwald % has pointed out that the semipermeable membranes may
possibly be permeable for only one class of ions, positive or negative,
and "not only the currents in muscles and nerves, but also the myste-
rious effects of electrical fishes might find their explanation by such
a property of the semipermeable membranes." Bernstein § and Briin-
ings || have recently adopted this view. Bernstein pointed out that,
in order to explain the above-mentioned current of action, a specific
permeability of the semipermeable membranes for cations must be
assumed. It is hardly possible that differences in electrical poten-
tial can arise in any other way in the tissues than by a separation of
anions and cations of the electrolytes dissolved in the tissues. As
the difference in the rate of diffusion for different ions always exists,
especially when acids or alkalies are formed, and as a difference of the
permeability of the protoplasm for oppositely charged ions may also
easily exist or arise, it is not difficult to understand that so many life
phenomena are accompanied by electrical changes and currents, e.g.
when light falls upon the retina, or when glands secrete.
Plants also show such currents, especially such plants, as are dis-
tinguished by a comparatively quick conduction of stimuli, e.g. Mimosa
or Drosera. This lends, perhaps, support to the idea expressed by
Hermann that the current of action is the cause, or means, of the propa-
gation of the nerve impulse. When a nerve or muscle is stimulated,
the stimulated spot becomes negatively electrical as compared with
the neighboring resting spot. In the next element of time this latter
spot becomes the seat of activity, and now becomes negative toward
the more distantly situated piece of nerve, etc. A region or wave of
negative potential is thus propagated from the original seat of stimu-
lation in both directions, through the nerve. Bernstein has found
that this negative wave is propagated with the same velocity as the
* Loeb, Science, N. S., Vol. 7, p. 154, 1898.
t Oker-Blom, Pfliiger's Archiv, Vol. 84, p. 191, 1901.
j Ostwald, Zeitsch. fur physik. Chemie, Vol. 6, 1890.
§ Bernstein, Pfliiger's Archiv, Vol. 92, p. 521, 1901.
II Briinings, Pfliiger's Archiv, Vol. 100, p. 367, 1903.
yo DYNAMICS OF LIVING MATTER
nerve impulse, so that there exists a possibility that this difference of
potential which originates upon stimulation is the cause, or the means,
of propagation for the nerve impulse. Hermann has given a more
detailed sketch of such an assumption.* The axis cylinder of the
nerve is surrounded by a liquid conductor of electricity, i.e. a solution of
electrolytes. If a certain element A of the axis cylinder be stimulated,
it will assume a negative charge, while the neighboring parts B assume
a positive charge. This leads to the formation of a microscopic cur-
rent from B through the liquid conductor to A. This current may
be considered as a stimulating current for the axis cylinder with an
anode at A and a cathode at B. We shall see in a later lecture that
if a current be made, the stimulation occurs at the cathode, while the
anode is put into a condition of diminished irritability. Therefore,
the region A now returns to a condition of rest, while B becomes active.
Then the same process is repeated for B and its neighboring element, etc.
Waller has been able to determine the beginning of life in the hen's
egg and in seeds of plants by galvanometric tests; he has also deter-
mined the cessation of life in the same manner, f These facts may
serve as a further indication that all life phenomena are accompanied
by electrical phenomena. We shall see later that salts play a great
role in life phenomena; and it is obvious that if changes in the nature
and number of ions in a solution accompany life phenomena, electrical
currents must also be a necessary consequence.
* Hermann, Handbuch der Physiologie, Vol. 2, 1st part, p. 193, 1879.
t Waller, C. P. de P Academic des Sciences, Vol. 131, pp. 485 and 1 173, 1900. Proceed-
ings of the Royal Society, Vol. 68, p. 79, 1901.
LECTURE V
THE ROLE OF ELECTROLYTES IN THE FORMATION AND PRES-
ERVATION OF LIVING MATTER
i. On the Specific Difference between the Nutritive Solu-
tions for Plants and Animals
The green plants are the factories in which the material for the
nutrition for animals and fungi is prepared. The green plant, how-
ever, manufactures also, as long as it grows, its own living matter out
of the electrolytes of the soil and the C02 of the air. The C02 is util-
ized for the formation of carbohydrates and probably fats; the salts
of ammonia, nitrates, phosphates, and sulphates are used for the
building up of nitrogenous compounds. One of the nutritive solutions *
which is most commonly used for phanerogamic plants is as follows : —
4 g. Ca(N03)2
i g. KN03
1 g. MgS04 + 7H20
1 g. KH2
0.5 g. KC1
1 g. KH2P04
The whole is dissolved in from 3 1. to 7 1. of water. A few drops
of ferric chloride are added to this solution. This solution may
vary within certain limits. It contains besides the anions C03, N03,
S04, and P04, which are necessary for the synthesis of the essential
compounds of the plant, the cations K, Ca, Mg, which do not seem
equally necessary for the synthesis of living matter. In addition to
these, free oxygen is absolutely necessary for the formation of living
matter in green plants.
For the fungi the nutritive solutions are similarly constituted, with
this difference only, that they cannot make carbohydrates of C02 ;
and they are therefore compelled to get their sugar from plants or
animals. If raised in a solution containing sugar or certain organic
acids {e.g. acetic, tartaric acids) and certain salts, they can also make
* Knop's Solution. See Pfeffer, Pflamenphysiologie, 2d edition, Vol. I, p. 413, 1897.
7i
72
DYNAMICS OF LIVING MATTER
all the constituents of living matter, e.g. fats, proteins, nucleins.
Raulin, a pupil of Pasteur, has investigated with unparalleled thor-
oughness the optimal nutritive solutions for a fungus, Aspergillus
niger. Raulin * determined which nutritive solution gave the great-
est development of living matter from a given quantity of spores, and
found that it possessed the following composition : —
Water .
.
1500 g.
Cane sugar
.
7° g-
Tartaric acid
i
4 g-
(NH4)3P04
•
0.60 g.
K2C03 .
>
0.60 g.
MgC03 .
>
0.40 g.
(NH4)2 S04
.
0-25 g-
ZnS04 .
.
0.07 g.
FeS04 .
.
0.07 g.
K2Si03 .
•
0.07 g.
Of course, to this list must be added atmospheric oxygen.
Part of the free acid in Raulin's solution is neutralized by the HO-
ions due to the presence of (NH4)3P04 and 1L2C03 in the solution.
The sugar, fatty acid, ammonia, S04, and P04 are used for the build-
ing up of living matter ; but it is not clear what the role of K, Mg, Zn, and
Fe is. It is remarkable that Ca is not required, and it seems to be a
general fact that Ca is not of great importance for the fungi, while it
is of great importance for animals, and apparently also for the higher
plants. But what is the role of the cations?
It has been noticed that the living tissues of plants, as well as of
animals, possess a selective power for certain salts, especially for K-salts.
Although in fresh-water streams the concentration of K-salts is often
very low, the plants which live in it are capable of storing up a com-
paratively large amount in their tissues. The muscle of animals shows
the same phenomenon, inasmuch as it contains a much higher per-
centage of potassium than the blood. This "selective power" admits
of only one explanation; namely, that the potassium is used for the
building up of more complex compounds in which the K cannot be
dissociated as a free ion. If a tissue utilizes one kind of metals in this
way, e.g. K, while another metal, e.g. Na, is chiefly used for the forma-
tion of dissociable compounds with Na as a free ion, the consequence
will be that the ashes of a tissue contain K and Na in altogether differ-
ent proportions from what they are contained in the surrounding solu-
* See Duclaux, Traite de microbiologic, Vol. I, p. 176, 1898.
ELECTROLYTES IN LIVING MATTER 73
tion. I think we may take it for granted that, at least, K forms a
nondissociable constituent of the protoplasm of a number of tissues of
animals and plants, and that it therefore may be considered a building
stone for living matter in the same sense as the above-mentioned anions.
This fact explains the so-called oligodynamic effects. This term
was applied to the fact that certain heavy metals like Cu, or, as I believe,
traces of their salts, can produce a toxic effect. Obviously the Cu-ions
form upon their entrance into the cell undissociable or practically
undissociable compounds with protein substances, and thus their con-
centration is kept lower in the cell than in the surrounding solution.
The consequence is that in due length of time enough Cu may diffuse
into the cell to act toxically. There is therefore no reason why we
should continue to set aside the oligodynamic effects as a distinct group
of phenomena in biology. It is quite possible that an ion may be
utilized in two ways by a tissue; namely, for the synthesis of mole-
cules from which it can no longer be dissociated as an ion, and in the
form of salts, — possibly ion-proteids, — where the metal can disso-
ciate as an ion.
What is true for the K may also be true for the Mg, but it can
scarcely be so for the Zn in Raulin's solution, although, curiously enough,
it is not so much less important for Aspergillus than K. Raulin found
that if he allowed spores to develop on the above-mentioned solution,
which contained all fourteen constituents, except K, the crop was only
one twenty-fifth of the dry weight of that which he got when he added
K. When the trace of Zn contained in that solution was omitted,
the dry weight of the crop was only one tenth of that which he obtained
when Zn was added. Raulin has made similar determinations for all
the constituents of his nutritive solution. The figure following each sub-
stance in the table below expresses how many times greater the dry weight
of the crop was with the addition of the substance than without it.
NH4 153
P04 182
Mg 91
K 25
S04 25
Zn 10
rc ••••••••o« — . ..
Si03 1.4
It was to be expected that the omission of NH4 from the solution would
reduce the crop considerably (to ^-3 of its weight), inasmuch as it
74 DYNAMICS OF LIVING MATTER
furnishes the material for the manufacture of the proteins. The P04
is needed for the nucleins, and it is probable that the Mg is necessary
for the building up of definite important compounds; but the Zn is
no part of any compound of the plant. It is therefore obvious that
the nutritive solution for a plant not only contains substances which
are of importance for the building up of its living matter, but also sub-
stances which do not enter into these compounds and are yet of im-
portance. I am inclined to believe that the explanation of the latter
facts takes us back to the antagonistic salt effects discussed in the
previous lecture.
If we compare the nutritive solutions for animals with those of plants,
we find in general that P04-, NH4-, N03-ions, which are of such im-
portance for plants, are either of no importance for animals, or are
directly poisonous, e.g. the NH4-ions. Inasmuch as the animals get
all their proteins and carbohydrates directly or indirectly from plants,
it is to be expected that they do not depend upon the C02 of the air
or the NH4, N03, or P04 of the soil. We meet, however, with another
striking difference between animals and plants, which was not to be
expected a priori; namely, the fact that Na, which appears neither
in Knop's solution for 'Phanerogams nor in Raulin's solution, is one
of the most, if not the most, important constituent of a nutritive solu-
tion for animals. Next in importance for animals is Ca, which does
not appear in Raulin's solution, although it seems to be important
for phanerogamic plants.
We have already seen that the majority of marine animals, e.g.
marine Gammarus, can only live in solutions which contain certain
salts, NaCl, CaCl2, KC1, and MgCl2 in definite proportions. The
lack of Mg is not so fatal as the lack of one of the other three
metals. One anion is sufficient; namely, CI. Without Na, K, or
Ca the animal lives at the utmost but a couple of hours, as a rule
a much shorter time; while in a mixture of NaCl, KC1, and CaCl2
it may live as long as two days, and still longer upon the addition
of MgCl2.
Similar results were obtained in experiments on the substances
which Tubularians need for regeneration and growth. These Hy-
droids can only live in a solution which contains NaCl, KC1, CaCl2,
and MgCl2. If one of these salts is lacking, no polyp can be regener-
ated. In order to allow the polyp to grow, a substance must be
added which keeps the reaction of the solution neutral; namely,
NaHC03*
The conditions for the development of the eggs of the sea urchin,
* Loeb, Pfiiiger's Archiv, Vol. 101, p. 340, 1904.
ELECTROLYTES IN LIVING MATTER 75
Strongylocentrotus purpuratus, are similar.* NaCl, KC1, and CaCl2
are necessary: as without one of these salts no segmentation is pos-
sible. For the complete development Mg and S04 are also required,
but these latter two constituents do not possess the same degree of
importance as Ca, Na, or K. In addition, a substance is needed which
keeps the solution neutral, e.g. NaHC03. Other constituents of the
sea water, such as P04, Fe, are not required. This latter statement
disagrees with the conclusions of Herbst.f
The same is true for Medusae : they will keep alive in solutions of
NaCl, KC1, CaCl2, MgCl2, in the proportion and concentration in
which these solutions occur in the sea water. In addition, a substance
is required which keeps the sea water neutral, e.g. NaHC03. I think
these examples may suffice as the proof of the fact that for marine
animals NaCl and CaCl2 and KC1 are essential for the maintenance
of life. It is questionable whether the substances which growing
animals require for the manufacture of living matter are taken from
the surrounding solution. Were this the case, only traces of any of
these salts should be sufficient, while in reality the proportion of Na,
K, and Ca can vary only within certain limits in the solution.
The tissues of marine animals seem to require a solution of the
same character. Dr. Rogers has, at my suggestion, determined in
which solution the heart of a marine crab beats longest. He found
that sea water is an excellent "nutritive" solution for the heart, and
that the same is true for a van't Hoff solution; namely, a solution of
100 molecules NaCl, 2.2 KC1, 2 CaCl2, 7.8 MgCl2, 3.8 MgS04. To this
should be added a trace of NaHC03. The action of sea water becomes
better if a little CaCl2 is added, possibly on account of a slight antago-
nistic effect between Ca and Mg.
It is remarkable that the tissues of fresh-water and land animals,
e.g. the frog, the tortoise, and apparently the mammals, live longest
in a solution which has the same constitution as the sea water, and
differs from the latter only in its concentration. The optimal concen-
tration of the solutions for frogs and land animals is about that of a
■x- solution of NaCl. In order to keep the isolated heart of cold-blooded
o
animals alive, Ringer has recommended the following solution : — %
* Loeb, Pflilger'ls Archiv, Vol. 103, p. 503, 1904.
f Herbst, Archiv fur Entwickelungsmechanik, Vol. 5, p. 649, 1897, and numerous other
papers on the same subject.-
Herbst did not recognize the antagonistic effects of salts, and so concluded that if the
elimination of one of the constituents of the sea water was injurious, this proved the neces-
sity of the omitted substance for the animal. The above-mentioned observations on Fundu-
lus show in my opinion the fallacy of this conclusion.
t Quoted after Rusch, Pfluger's Archiv, Vol. 73, p. 535, 1898.
y6 DYNAMICS OF LIVING MATTER
Water iooo g.
NaCl 6 g.
KC1 0-075 g-
CaCL, 0.1 g.
NaHC03 0.1 g.
Rusch has applied this solution with success for the isolated heart
of warm-blooded animals, with the difference only that he added 8 g.
instead of 6 g. of NaCl to 1000 g. of water.
Locke * recommends the following solution for the isolated heart
of the rabbit: —
Water 1000 g.
NaCl 9.10 g.
KC1 . . . , . „ . . 0.2 g.
CaCL, 0.2 g.
NaHC03 0.1 g.
The solution is said to be more effective if a little dextrose is added,
e-g- 1 g-
Otherwise Locke's solution differs from Ringer's by a somewhat
higher amount of KC1 and CaCL,. His figures for these latter salts
are approximately those which Abderhalden found for the concen-
tration of these salts in the serum of rabbits; namely, 0.024 Per cent
CaCl2 and 0.042 per cent KCl.f
If we express the percentage solutions of Ringer, Locke, or Abder-
halden, in the values of grammolecular solutions, we find that it is
approximately 100 molecules NaCl to 2 molecules of CaCL,. This
is practically the proportion in which these salts exist in the sea water,
and in which marine animals live longest. This proportion may vary
a little for marine animals, and the same is true for the solutions in
which the tissues of animals live best, as a comparison of the figures
of Ringer and Locke shows.
An observation mentioned already in a former lecture shows con-
clusively that the mixture of 100 NaCl, 2 KC1, and 2 CaCl2 cannot be
considered as a nutritive solution for animals, but must play a different
role. Fundulus lives just as well in distilled water as in sea water.
This fact proves that these animals do not depend for their nutrition
* Locke, Centralblatt filr Physiologie, Vol. 14, p. 670, 1901.
t The fact that Locke also mentions sugar as one of the necessary constituents of his
solution indicates that he considers the other constituents also as nutritive material. This
would, however, be wrong. From my own experiments I do not think that the addition of
sugar is of any value.
ELECTROLYTES IN LIVING MATTER JJ
and development upon the salts dissolved in the sea water. If the
young fish, however, are put into a pure solution of NaCl of the concen-
tration in which this salt is contained in the sea water ( — J, the animal
dies in less than twelve hours. If CaCl2 is added, the animal does not
live more than twenty-four hours. If it is desired to keep animals
alive permanently, — my experiments lasted for ten days, — not only
2 CaCL, but also 2 KC1 must be added to 100 NaCl. This is exactly the
solution which is generally considered as a nutritive solution for animals.*
I believe that these facts show that we must discriminate between
nutritive and protective solutions. Ringer's solution, as well as the
sea water, are primarily protective and not nutritive solutions. What
is meant by this becomes clear if we remember what was said concern-
ing the antagonistic effects of salt. A — solution of NaCl, as well as a
m
7- solution of ZnSCX, alone are each poisonous for the eggs of Fundulus.
64
If mixed, the solution becomes considerably less poisonous. It is prob-
able that these two salts if together in solution materially diminish
their rate of diffusion into the tissues. It follows from these experi-
ments that the role of the Ca and Mg in the sea water, as well as in a
Ringer's solution, consists partly in antagonizing the effects which would
be produced by the NaCl were it alone in solution. The experiments
with Fundulus suggest that in this case the presence of the Ca and Mg
in the sea water diminishes the rapidity of diffusion of the NaCl into
the tissues. It is possible that the Zn acts in some protective way in
the case of Raulin's solution, although in regard to this it is not
possible to make a definite statement.
But there remains the other fact that K is also needed. The life
of Gammarus and many other marine animals is not essentially pro-
longed by the addition of CaCl2 or MgCL, or both to the NaCl solution,
but is materially prolonged by the addition of CaCl2 and KC1 to the
NaCl solutions. Besides we cannot, in general, substitute any other
bivalent metal (with the exception of Sr) for Ca ; nor can we sub-
stitute any other univalent cations for Na and K. This indicates
that the metals Na, Ca, K, and Mg play a role in life phenomena other
than that of serving for the synthesis of living matter, and also other
than that of merely regulating the velocity of diffusion. We have
already alluded to the possibility of their necessity for phenomena of
secretion. We are inclined to believe that what is generally called
irritability and contractility is due to the influence of these ions.
* Loeb, Pfluger's Archiv, Vol. 55, p. 530, 1893.
7% DYNAMICS OF LIVING MATTER
2. Concerning a Theory of Irritability and the Role of Na,
K, and Ca for Animal Life
In 1899 I outlined a general theory of irritability which may be
briefly summarized in the following sentences which I quote from a
former paper: "The salts, or electrolytes in general, do not exist in
living tissues as such exclusively, but are partly in combination with
proteids (or fatty acids). The salts or electrolytes do not enter into this
combination as a whole, but through their ions. The great importance
of these ion-proteid compounds (or soaps) lies in the fact that, by the
substitution of one ion for another, the physical properties of the
proteid compounds change (e.g. their surface tension, their power to
absorb water, or their viscosity or state of matter). We thus possess
in these ion-proteid or soap compounds essential constituents of living
matter, which can be modified at desire, and hence enable us to vary
and control the life phenomena themselves."*
Life phenomena, and especially irritability, depend "on the pres-
ence in the tissues of a number of various metal proteids, or soaps (Na,
Ca, K, and Mg), in definite proportions."
I first applied this conception to a phenomenon which had hitherto
been observed only occasionally ; namely, rhythmical contraction of the
muscles of the skeleton. f I found that such rhythmical contractions
occur only in solutions of electrolytes, i.e. in compounds which are
capable of ionization. In solutions of nonconductors .(urea, various
sugars, and glycerine), these rhythmical contractions are entirely or
practically impossible. Only in certain, not in all, salt solutions are
such rhythmical contractions possible. All the solutions of Na-salts
are able to produce them, but in a 0.7 per cent NaCl solution, contrac-
tions begin later, and are less powerful, than in an equimolecular
NaBr solution. The experiments on the rhythmical contractions of the
muscles of the skeleton led to some other data concerning the effects
of those salts. Solutions of Na-salts produce rhythmical contractions
only if the muscle cells contain Ca-ions in sufficient numbers. As soon
as there is a lack of Ca-ions in the tissues, the Na-ions are no longer
able to cause rhythmical contractions. On the other hand, if we add
Ca-salts in sufficient quantity to the NaCl solution, it will no longer
cause rhythmical contraction in a fresh muscle of the frog. It there-
* Loeb, Am. Jour. Physiology, Vol. 3, p. 337, 1900.
t Loeb, Festschrift fur Professor Fick, Wurzburg, 1899.
The idea of the general existence of such ion-proteid compounds was developed inde-
pendently by Pauli and myself in 1899. Loeb, Pfliiger's Archiv, Vol. 75, p. 303, 1899 ; and
Festschrift fur Fick, 1899 ; and W. Pauli, Wiener akademischer Anzeiger, October 12, 1899 ;
and Ueber physikalisch-chemische Methode7i und Probleme in der Medizin, Wien, 1900.
ELECTROLYTES IN LIVING MATTER 79
fore looks as if the presence of a certain quantity of Na-ions caused
contractions ; but if the quantity of the Na-ions becomes too great
in proportion to the Ca-ions, the muscle loses its irritability. On the
other hand, if there are too many Ca-ions present, the rhythmical con-
tractions become also impossible. The quotient of the concentration
of the Na-ions over the concentration of the Ca-ions, -^-a, becomes
Cca
therefore of importance for phenomena of irritability. We shall see
later that Mg acts very much like Ca in this respect.
It is hardly necessary to mention that this suggested the possibility
that muscular contraction, in general, is due to a substitution of Na
for Ca, or vice versa, in certain compounds (proteins or soaps) in the
muscle. Every substance or agency will act as a stimulant which
brings about such a change of the metals in these compounds in the
muscle.
It may be added that all the salts of univalent metals act like the
Na- salts, inasmuch as they cause rhythmical contractions when the
muscle is put into them. All these salts, however, have secondary
effects which usually prevent the contraction from lasting as long as
in NaCl. In KC1 the muscle gives only a few twitches when thrown
into the solution, and then stops. In LiCl the twitches may last over
a day. As of the salts with a univalent metal, only the Na- and K-salts
occur in the muscle, only the substitution of one of these salts need be
considered for the theory of irritability.
Not only Ca- but also Sr- and Mg-salts are capable of antagonizing
the stimulating effects of a pure NaCl solution when added to the
same. As I stated six years ago, we owe it to the Ca- and Mg-salts
in our blood that our skeletal muscles do not contract rhythmically
like our heart.
We may now give a provisional answer to the question why it is
that the Na-salts, which are unnecessary in the nutritive solution of a
plant, become of so great importance for the life of an animal. If
our hypothesis be correct, the answer should be that all the muscular
contractions are due to a substitution of Na-(or K) for Ca- or Mg-ions,
or vice versa. In the plant, which has no muscles, there is no need for
any NaCl. Likewise we can understand why CaCLj plays a lesser
role in plants than in animals, as Raulin's investigations indicate.
ft
In an - solution of NaCl it requires, as a rule, a long time — an
8
hour or more — before the contractions begin at ordinary room tem-
perature ; while in a more concentrated solution the contractions begin
more rapidly. I concluded from this that a NaCl solution produces
80 DYNAMICS OF LIVING MATTER
this effect only through the diffusion of NaCl into the muscle. As
soon as the concentration of the NaCl or the Na-ions in the muscle
has reached a certain value, the muscle fiber will begin to contract.
C -
Normally the quotient — — in the muscle is too small to permit such
contractions. The addition of a slight amount of NaHO accelerates
the process, possibly by accelerating the diffusion of the salt into the
muscle.*
The fact that CaCl2 inhibits the rhythmical contractions which are
produced by the NaCl, suggested experiments on the effects of salts
which precipitate Ca or diminish the concentration of free Ca-ions
through the formation of salts with a low degree of dissociation. It
was found that such salts, e.g. sodium-oxalate, -fluoride, -citrate, and
-tartrate, act much more powerfully than NaCl or sodium-acetate or
-succinate. If such salts be applied to the nerve they produce before
the twitchings begin a condition of increased irritability, comparable
to the catelectrotonic condition caused by the constant current at the
region of the cathode.t
The addition of a slight amount of acid to a -z NaCl solution shortens
o
the latent period for the beginning of the rhythmical contractions.
We shall see later on that the acid acts possibly like the above-mentioned
salts; namely, by liberating the calcium from certain organic combi-
nations in the muscle or nerve. Inasmuch as COa is produced in the
muscle itself, this relation is of importance.
These facts suggested the idea that the process of contraction is
caused by an exchange of Na or K for Ca or Mg, or vice versa, in cer-
tain compounds in the muscle (or nerve). This change must be accom-
panied by a change in some physical property of the compound, e.g.
the surface tension, the state of aggregation, viscosity, absorbing power
for water, etc. The change in such a physical property may deter-
mine or facilitate the process of contraction.
I applied the facts found in the muscle to the study of rhythmical
contractions in a more favorable object; namely, the swimming
bell of the Medusa. The jellyfish is comparable to a free-swimming
heart which beats rhythmically, with this difference, however, that the
jellyfish does not beat incessantly, like the heart, but intermittently,
with long pauses between series of contractions. It is known that the
central nervous system of the Hydromedusa is situated in a ring near
the edge of the Medusa. Romanes had already observed that if the
* Loeb, Festschrift filr Fick, Wiirzburg, 1899.
t Loeb, Am. Jour. Physiology, Vol. 5, p. 362, 1901. Pfiuger's Archiv, Vol. 91, p. 248,
1902.
ELECTROLYTES IN LIVING MATTER 8 1
edge of a Hydromedusa be cut off from the center, the former continues
to beat while the latter stops beating. This fact was utilized as an
argument to prove that the contractions in a Medusa originate normally
from the nerves in the margin. This may be so, but it seemed to me
that the center of a Medusa (deprived of its nerve ring) might also be
able to beat if it were not prevented from so doing by the constitution
of the sea water. I found, indeed, that the isolated center of Gonio-
nemus, a Hydromedusa, common at Woods Hole, is able to beat rhyth-
mically in a pure solution of NaCl.* The center beats in such a solu-
tion very rapidly, and the more rapidly the higher, within certain limits,
the concentration of the NaCl solution. The addition of a small quan-
tity of CaCl2 or MgCl2 retards or inhibits the contractions caused in
the NaCl solution. If a salt which precipitates Ca or diminishes the
concentration of its ions is added in excess to sea water (e.g. sodium
oxalate, fluoride, citrate), the center can be caused to beat in sea water
also.
It is thus obvious that the case of the center of the Medusa seems
very analogous to that of the muscle. Just as the latter is prevented
from twitching in the blood on account of the presence of CaCl2 and
MgCl2, so the isolated center of Gonionemus is prevented from beat-
ing in sea water on account of the presence of CaCl2 and MgCl2.
After these data had been obtained I asked Dr. Lingle to deter-
mine whether similar laws hold for the heartbeat. It was known that
if the sinus venosus of a frog's heart be severed from the heart, the
former goes on beating as before ; while the rest of the heart, especially
the isolated ventricle, stops beating in blood. This observation is
comparable to the one made by Romanes on jellyfish; and we may
carry the analogy a step farther, by comparing the center of the Medusa
to the ventricle ; the edge to the sinus venosus of a frog's heart. Lingle
worked on the heart of a tortoise. f He found that the ventricle is only
able to beat after it has been put for about half an hour into a pure
solution of NaCl. When the ventricle remains permanently in the
sodium chloride solution, the heartbeats will stop after a certain time,
as Lingle believes, on account of the diffusion of too much NaCl into
the heart muscle. If the strip of the ventricle is put into a moist chamber
after the beats are once started in a NaCl solution, they may continue
for a number of days, until the process of putrefaction puts an end to
the contraction. No other substance can take the place of Na. Li,
which acted so well in the case of the isolated frog's muscle, can be
only partially substituted for NaCl. One of the most remarkable
* Loeb, Am. Jour. Physiology, Vol. 3, p. 383, 1900.
t D. J. Lingle, Am. Jour. Physiology, Vol. 4, p. 265, 1900 ; Vol. 8, p. 75, 1902.
G
82 DYNAMICS OF LIVING MATTER
facts which Dr. Lingle found is that even the heart stimulants, such as
caffeine, cannot cause the strip to beat, except in the presence of NaCl.
These experiments give the impression that the ventricle of the tor-
toise does not beat in the blood, because of the fact that the NaCl in
the blood is prevented from entering into the heart cells or from acting
upon them through the presence of another salt; namely, CaCl2, or
MgCl2, or both.
These experiments show that in order to start the heartbeat, a pure
NaCl solution, or a pure solution of an Na-salt, is required; but if
the heart remains permanently in a pure NaCl solution, it stops beating.
The pure solution of NaCl acts like a poison. If, however, a small
amount of CaCl2 be added to the NaCl solution after the heartbeats
have once started, the beats can go on for a long time. They can also
continue in serum after they are once started in a pure NaCl solution.
The addition of Ca therefore acts antagonistically to the injurious
action of the pure NaCl solution. Ca cannot start rhythmical con-
tractions in the ventricle, but it is necessary to sustain the rhythmical
action once started by NaCl. It is possible again that the pure NaCl
solution becomes toxic through the fact that in such a solution too
many Na-ions take the place of Ca, in the ion-colloids, and that this
is prevented by the presence of a trace of Ca. It is possible that the
Ca prevents or retards the diffusion of Na into the muscle. In a pure
NaCl solution, however, the rhythmical action of the heart strip can
also be sustained for a long time without the addition of Ca, if pure O
is allowed to bubble through the NaCl solution, or if a trace of H202
is added to the solution. I consider these observations of the greatest
importance, inasmuch as they show that the processes of oxidation
going on in the muscle give the latter equal protection against the NaCl
poisoning, just as the addition of CaCl2 to the NaCl solution. Could
it be possible that the increase in oxidations leads to the setting free of
Ca inside the muscle, and that the Ca acts in this case?
When I entered upon the investigation of the effect of salts on the
rhythmical contractions of the muscle, I had in mind the solution of
the problem of electrical stimulation. Previous experiments on the
effects of the galvanic current had led me to the idea that the polar
effects of the current are due to the ions which are blocked in their prog-
ress by the semipermeable membranes in these organs; and my idea
was that experiments with salts would show which ions are responsible
for the effects of a galvanic current. If the hypothesis that ions are
responsible for the stimulating effects of a current were correct, it was
to be expected that in solutions of nonconductors no twitchings would
occur. One of the first facts that I ascertained was that this idea was
ELECTROLYTES IN LIVING MATTER 83
generally correct. In solutions of dextrose, cane sugar, milk sugar,
and glycerine, no twitchings of the common muscles occurred, no
matter how concentrated the solution. In solutions of urea the same
was true, in general, but occasionally transitory contractions were
observed. In alcohol I also observed occasionally a slight twitching,
but it is possible that in these latter cases the twitchings were caused
by an indirect effect of urea and alcohol upon reactions or changes
inside the muscle fibers. On the whole, I am under the impression
that the muscle cannot be, or only exceptionally, and to a slight extent,
caused to contract by solutions of nonconductors. I found that the
same is true for the rhythmical contractions of the center of the jelly-
fish (Gonionemus). Dr. Lingle tried the same experiments on the
strips from the ventricle of the tortoise, with the same result. In pure
solutions of dextrose, cane sugar, and glycerine, no beats originated,
even if the strip remained in these solutions for a day; but when the
ventricle was afterward put into a pure NaCl solution the contrac-
tions began, showing that these solutions had only prevented the
contractions without permanently injuring the heart. Lingle also de-
termined what the minimum concentration of NaCl was that was able
n
to start heartbeats. He found that in a mixture of 98 c.c. - cane sugar
+ 2 c.c. - NaCl, or 96 c.c. - cane sugar + 4 c.c. - NaCl, no beats
84 8
ft 71
started; while with 90 c.c. - cane sugar +10 c.c. - NaCl beats could
be produced.
All these experiments seemed to support or, at least, not to contra-
dict the idea set forth in my first paper on this subject, that the rhythmical
contractions depend upon the exchange of Na (or K) and Ca (or Mg) in
certain compounds, possibly proteids or soaps, in the muscle. Such an
exchange might alter the physical properties, e.g. the surface tension,
or viscosity, etc., of the substance; and a sudden change in one of the
properties might result in a change of form such as underlies contrac-
tion. I figured to myself that the change starting rhythmical contrac-
tions was a sudden change in surface tension, e.g. a phenomenon of
spreading, and gave expression to this possibility in my book on Brain
Physiology. A series of new observations confirms me in the idea
that we are dealing here with phenomena which must occur at the
surface of the elements.
In 1 90 1 I described a form of irritability in the muscle which, to my
knowledge, had never been noticed before, and which is produced by
such salts as precipitate Ca or diminish the concentration of free Ca-ions,
such as citrates, oxalates, fluorides, carbonates, phosphates, etc., and
84
DYNAMICS OF LIVING MATTER
especially the sodium salts of these acids.* The experiment is as
/VYt
follows: If the gastrocnemius of a frog is put into a — solution of
o
sodium citrate and left there for two or three minutes, it will go into
powerful tetanic contractions or rather cramplike clonic contractions
when taken out of the solution; while these contractions stop at once
when the muscle is put back immediately. This can be repeated at desire,
the muscle always going into contractions when exposed to the air, and
relaxing again when put back into the solution. Zoethout found that
this reaction can be produced quicker and with greater certainty when
a slight amount of a K-salt is added to the solution. I believe that the
K antagonizes the tendency to rhythmical contractions which the muscle
possesses in a sodium-citrate solution. It seems to be necessary that
this tendency to rhythmical
contractions be overcome in
order to obtain the phenomenon
which we are now discussing,
and which I called in a pre-
liminary way the contact re-
action of muscle, inasmuch as
it can be produced by changing
the nature of the medium which
surrounds the muscle. The
apparatus used for the demon-
stration of this experiment is
shown in Fig. 15.
When only part of the
muscle is lifted out of the
citrate solution, only those fibers
go into tonic contraction which
are in contact with the air;
while those fibers which remain
in the solution do not contract.
The reaction, therefore, is a
purely local one in each in-
dividual muscle cell. This re-
action not only occurs when
the muscle is brought from the
solution into contact with air,
but also when it is brought into contact with C02, oil, toluol, sugar,
or glycerine solutions. All these solutions are nonconductors, and
* Loeb, Am. Jour. Phydology, Vol. 5, p. 362, 1901.
Fig. 15.
ELECTROLYTES IJV LIVING MATTER 85
I at first believed that I was dealing here only with a break shock
caused by the muscle's own current; but this was contradicted by
various facts: first, that only those individual fibers contracted which
were lifted out of the solution, while the others remained relaxed;
second, that the latent period for the contraction after the muscle
has left the solution is too long; namely, as much as a second
or more. The most convincing proofs against such an assumption
are, however, the following facts. The irritability of the muscle for
the contact reaction does not reach its maximum at once, but only
after a certain time. When the sensitiveness of the muscle has reached
its height, a glycerine or a sugar solution can be substituted for
the citrate solution. Whenever the muscle is at that time taken out
from the glycerine or sugar solution and brought into contact with
the air, the contraction occurs; while it ceases when the muscle is put
back into the sugar solution. After a short time, however, the muscle
loses its contact irritability in the sugar or glycerine solution. These
experiments, however, certainly prove that the contact reaction is not a
break shock caused by the resting current of the muscle itself when it
is lifted out of the citrate solution.
It is a very interesting and theoretically important fact that the
muscle loses this peculiar form of irritability very soon when it remains
in contact with air, oil, sugar solution, glycerine, or salt solutions,
different from those that produce this specific irritability. In LiCl or
NaCl solutions the contact irritability is lost as fast, if not faster, than
in a sugar or glycerine solution. We can reestablish the irritability,
however, by putting the muscle back into the sodium citrate solution
for some time. This fact, together with those mentioned before, suggests
the following as the most probable explanation of the peculiar phenomena
of contraction with which we are dealing in this case. The solutions
which produce the contact irritability possess anions which are liable
to form insoluble calcium compounds. Whatever the effects of these
anions may be, the fact that in less than a minute the contact effects are
noticeable, indicates that only the surface layer of the muscle, or the
surface layer of each individual fiber, is altered. It is impossible for
the anions to migrate deeper into the muscle in so short a time. In
the surface layer of the muscle or the individual fibers, we have there-
fore temporarily a diminution of Ca-ions. We have then a muscle
whose surface layer differs from that of an ordinary excised muscle.
If this layer is once established, the muscle contracts at any change from
the citrate, carbonate, fluoride, etc., solutions to air, C02, oil, 2 n sugar
solution, glycerine, chloroform, or toluol. If the muscle be left in these
media, or put into a NaCl or a CaCL, solution, it loses this contact
86 DYNAMICS OF LIVING MATTER
irritability. This loss of contact irritability of the muscle in air, oil, etc.,
may be due to the migration of Ca-ions from the interior of the fiber
or muscle to the surface, thus reestablishing approximately the original
normal surface condition. If we then put the muscle back for a short
time into a sodium citrate or sodium fluoride, etc., solution, a diminu-
tion of Ca-ions will again occur in the surface layers, and the contact
irritability will be reestablished. As we should expect, the length of
time that the muscle remains in the solution is as important as the
concentration of the solution. If we dip a muscle for a few seconds
only' into a sodium citrate solution (i-g. molecule in 10 1.) the
contact irritability cannot be produced, as there is not time for a large
enough number of citrate-ions to enter the muscle.
Dr. Zoethout carried these investigations still farther. He found
that if a muscle be put into a pure - solution of any potassium salt,
e.g. KC1, KN03, KI, K2S04, K-oxalate, etc., the tone of a muscle
increases, i.e. the muscle shortens while it is in the solution. If, however,
the muscle is put into a pure ^ CaCl2 or NaCl solution, it again relaxes*
The minimum concentration of KC1 for bringing about this increase
in tone of the gastrocnemius of a frog was 1 c.c. — KCl + 9 c.c. H20 or
— glycerine. If, however, a potassium salt was chosen whose anion
8
is liable to decalcify the muscle, the minimum concentration could be
less. Thus J c.c. ^ K-citrate + o^- c.c. H20 was already effective.
o
Zoethout interprets this as showing that the Ca-ions of the muscle itself
are liable to antagonize the shortening action of the K-ions. This
interpretation he supported by a number of experiments. "It occurred
to me that since potassium increases the tone of the muscle and calcium
inhibits this action of the potassium, it might be possible that the pre-
cipitation of the calcium salts causes contact irritability, becauses it
destroys the normal equilibrium between these two salts in the muscle. "
" Upon testing this view we found it to be correct. The contact reaction
produced by sodium citrate is increased if we previously, or simul-
taneously, introduce K-ions into the muscle. " t Zoethout's conclusions
are as follows: "If the calcium salts in the muscle are decreased, the
efficiency of the K-ions to increase the tone of the muscle is increased.
If the K-ions in the muscle are increased, the efficiency of such salts
as Na-oxalate and Na-citrate to cause contact irritability is increased.
* Zoethout, Am. Jour. Physiology, Vol. 7, p. 199, 1902.
t Zoethout, Am. Jour. Physiology, Vol. 7, p. 320, 1902.
ELECTROLYTES IN LIVING MATTER 87
The contact irritability depends (as Loeb suggested) on the disturbance
of the normal ratio of salts in the muscle. Perhaps it is the disturbed
ratio between the potassium and calcium salts which makes the contact
reaction possible." Of course the experiment of Zoethout does not
explain why the contact reaction only occurs when the muscle is taken
out of the citrate solution.
I am inclined to believe that not only the K but also the Na-salts
are concerned in this reaction ; but it is certain that Zoethout' s observa-
tions establish the fact that the antagonism between K and Ca-salts
is to be considered in the theory of animal irritability and stimulation.
The statement contained in my older publications, namely, that
possibly the substitution of Na for Ca, or vice versa, caused the twitch-
ing of the muscle must be modified so as to include also the substitution
of K for Ca, or vice versa. Perhaps it may be said that the substitution
of any univalent cation for Ca in the muscle, or vice versa, causes a
twitching. As of the univalent metals, however, only Na and K occur
in the tissues, they are the principal ones to be considered. It seems
from these observations and others, all of which cannot be considered
in this short sketch, as if indeed the substitution of Na or K for Ca-salts,
or vice versa, is the essential feature of the twitching or of muscular
stimulation. It would be of the utmost importance to determine which
of the two possible changes was the real cause. We know that in general
a substitution of Ca for K or Na in colloids favors the formation of
more solid or insoluble compounds, e.g. in the case of soaps. In the
case of the coagulation of blood or milk, it is also obvious that Ca in
moderate quantities favors coagulation.
Ringer had already observed that barium salts have a stimulating
effect upon muscle, and I have been able to confirm this observation.
A pure solution of any soluble barium salts gives rise to powerful rhyth-
mical contractions of the muscle ; and the threshold for this stimulation
is much lower for Ba than for the corresponding Na-salts. In a NaCl
solution the contractions last longer than in a BaCL, solution, on account
of the greater toxicity of the BaCl2. I expected from this that a pure
solution of CaCl2 or SrCl2 might act similarly to BaCl2, but this does
not seem to be the case for the muscle. Two years ago, however, I
found some new facts concerning the influence of salts upon rhythmical
contractions of the center of a Calif ornian jellyfish, Poly orchis, which
meet this expectation.* If the margin containing the central nervous
system of this Medusa be cut off from the center of the swimming bell,
the center no longer contracts spontaneously in sea water; nor if it
be put into a pure NaCl solution of about the concentration of the
* Not yet published.
88 DYNAMICS OF LIVING MATTER
sea water do contractions begin. It differs in this regard very markedly
from Gonionemus, whose center begins to beat at once in a pure NaCl
solution. After a certain time, however, generally a number of hours,
rhythmical contractions will begin in the isolated center of Polyorchis
in a pure NaCl solution, and may last with long interruptions for two
or three days. When they have ceased in a pure NaCl solution, a few
single contractions can at any time be produced by touching the subum-
brella with a drop of a solution of a potassium salt; but the addition
of a potassium salt to the NaCl solution, although it promptly calls
forth a single contraction or a short series of contractions, does not
maintain the rhythm.
A sure means of producing rhythmical contractions of the isolated
center of Polyorchis at once in a pure NaCl solution is the addition of
a certain amount of a salt which precipitates Ca, or diminishes the
concentration of the Ca-ions, e.g. Na-citrate, -tartrate, -oxalate, etc.
I generally used the citrate as it seems to be the least harmful. If
10 c.c. of a m sodium citrate solution be added to a ioo c.c. | n NaCl
solution, rhythmical contractions of the isolated center begin usually
at once, and may last an hour or more. A second means of calling forth
rhythmical contractions in a pure solution of NaCl at once is the addi-
tion of a trace of an acid, e.g. HC1. C02 acts in the same way, and I
have wondered whether this acid which is formed regularly in the body
does not thus play an important role in rhythmical contractions in
general. The addition of acids may even cause the center to beat in
sea water. About 1.5 to 2 c.c — HC1 to 100 c.c. of sea water is required
for this purpose. Alkalis have the opposite effect. The action of the
acid may be the same as that of the oxalate and citrate; namely, to
set free Ca, which is in organic combinations in the cells, or at the surface
of the cells, and make thus a substitution of Na or K for Ca, or vice
versa, in these organic compounds, possible. It may be mentioned
here that the oxalates, citrates, and similar salts, and the acids, are
believed to play such a role in the process of the coagulation of milk.*
One of the promptest means of producing rhythmical contractions in
the isolated center of Polyorchis is putting it into a pure solution of
CaCl2, BaCl2, or SrCl2. Instead of dissolving the CaCl2 in distilled
*YYh
water, it may be dissolved in a | m or — sugar solution in order to have
a solution which is more nearly isosmotic with sea water. If an isolated
center is put into a solution of 10 c.c. f m CaCL, + 50 c.c. | m cane sugar
* A. S. Loevenhart, Hoppe-Seyler's Zeitschr. fur physiologische Ckemie, Vol. 41, p. 177,
1904.
ELECTROLYTES IN LIVING MATTER 89
or into 10 c.c. f m CaCl2 + 50 c.c. distilled water, the center usually
begins to beat rhythmically. The rhythmical contractions may last
for three hours or more. Such rhythmical contractions can even be
caused in a center which has been washed and kept for three hours in a
pure solution of cane sugar, to make sure that the sea water at the surface
of the muscle cells has been entirely removed. In this case, however,
the contractions do not last as long, inasmuch as a solution of cane
sugar as well as a pure CaCL, solution are injurious to the muscle.
BaCL, is much more effective than CaCl2, as it requires a much lower
concentration of BaCl2 than of CaCl2 to produce rhythmical contractions
in an isolated center of Polyorchis. Even in a solution of \ c.c. | m
BaCl2 + 50 c.c. § m cane sugar, rhythmical contractions were produced
which lasted about nine minutes. SrCl2 is much less toxic than BaCl2
and it acts more like CaCl2.
If it be true that the exchange of Ca for Na or K, or vice versa, in
certain organic combinations be the cause of these rhythmical contrac-
tions, we are apparently confronted with conflicting facts ; namely,
that Ca-salts, as well as salts which precipitate Ca, produce rhyth-
mical contractions; but the facts are no more in conflict in this case
than in the similar case of the coagulation of milk, where both a previous
treatment of the milk with decalcifying salts or acid, as well as the
addition of a soluble calcium salt, favor coagulation. In this case the
probable explanation, according to Loevenhart, is that a soluble calcium
salt is necessary for the coagulation. This calcium salt may be added
from without, or may be obtained from the milk itself, by freeing it from
a combination in which it is held there. The same may be true for the
rhythmical contractions in the center of Polyorchis. In order that a
contraction may occur, the formation of a certain calcium compound
(soap or a calcium proteid ?) is required. This condition may be satis-
fied by the diffusion of calcium into the cells from without, or by cal-
cium being freed from certain other compounds within the muscle cells
themselves (by acid, certain salts, like the oxalates or citrates or, as we
shall see later, by the action of enzymes). The process of contraction
is due to the substitution of Na or K for the Ca, or vice versa. Ba
and Sr act like Ca.
Why is it that the isolated center of Polyorchis does not contract
rhythmically in normal sea water? If CaCl2 acts as a stimulus, it is
not probable that it is the CaCl2 of the sea water which inhibits its
contraction. It might be possible that the action of the CaCl2 in the
sea water is antagonized by the NaCl. There seems to be indeed a
certain antagonism, inasmuch as it is easier to produce rhythmical
contractions in a pure solution of CaCl2 or in a solution of CaCl2 in cane
90 DYNAMICS OF LIVING MATTER
sugar, than in a mixture of CaCL, and NaCl solutions ; * but the antagonism
is not complete, and I have actually obtained contractions in a mixture
of NaCl + CaCl2 in a center of Polyorchis. It can be shown that the
Mg-salts contained in the sea water inhibit the muscular contractions.
If we start rhythmical contractions in a mixture of 50 c.c. f m NaCl +
10 c.c. m Na-citrate, and then put the center into a pure NaCl solution,
or a solution of 50 c.c. NaCl + 1 or 2 c.c. CaCl2, the center continues to
contract. If, however, the center be put into a solution of 50 c.c. f m
NaCl + 5 c.c. f m MgCl2 the contractions are inhibited. I believe that
it is generally more due to the MgCl2 than to the CaCL, that an isolated
center of a Medusa does not beat in normal sea water.
The facts thus far described give no clear answer to the question
whether the substitution of NaCl or KC1 for CaCl2 or the reverse process
causes the contraction. Possibly the following observation may throw
light on this problem: If an isolated center is put into 50 c.c. f m cane
sugar + 10 c.c. § m CaCl2 contractions will begin, which continue when
the center is put into 50 c.c. f m cane sugar 4- 10 c.c. m sodium citrate;
but if the center is put from the latter into the former solution, it stops
beating at least for some time. Various modifications of this experiment
give similar results: they seem to speak in favor of the idea that the
substitution of Na or K for Ca causes a contraction ; but the evidence is
by no means unequivocal.
The question may be asked how it happens that in a pure solution
of NaCl the beats do not start at once, but only after a number of hours.
Is it necessary that NaCl enter the cells of the Medusa, and that this
process requires time? Were this the reason, we should expect that
within certain limits an increase in the concentration of the NaCl solu-
tion should accelerate the beginning of the contractions. I have not
been able to find that this is true. The contractions began about
equally late in a |- m and a -§-,§, or | m NaCl solution. I am more
inclined to believe that the Ca must enter into an appropriate com-
bination in the muscles, and, for that purpose, must be freed from
another combination which is responsible for the delay in the beginning
of the spontaneous contractions of the center of Polyorchis in a pure
NaCl solution. The beats of the center begin in a pure NaCl solution
when the muscle cells of the center have had time to free an abundant
amount of calcium from an organic combination contained in them.
This might be done by a hydrolytic enzyme directly or indirectly, in
the latter case through the influence of an acid, e.g. C02, in the muscle
cells. This supposition has its analogue in the action of rennet in the
* It is possible that this antagonism is due to the fact that the NaCl and CaCl2 retard
each other's diffusion into the cells.
ELECTROLYTES IN LIVING MATTER 91
coagulation of milk, where this enzyme seems solely concerned in ren-
dering available Ca, which naturally is held in organic combination in
the milk in such a form as to be of no use for the process of coagulation.*
A word may be said in regard to the difference in the behavior of the
isolated center of Gonionemus and Polyorchis toward a pure solution
of NaCl. The former begins to beat in such a solution almost instantly,
the other as a rule only after a long interval. The difference may con-
sist simply in the fact that the cells of Gonionemus have from the start
enough Ca in an available form, while this is not the case in Polyorchis.
In the case of the former, the beats can begin immediately in a pure
NaCl solution, while in the latter this is not possible.
The question may now be asked, What keeps the normal heart
beat or the normal contractions of the jellyfish going? I believe the
conditions are the same as those discussed in muscles, the strips of ven-
tricle, or the center of the Medusa, with this difference only, that the
salts or ions, which according to our hypothesis are needed for that
purpose, are all supplied from within. I am inclined to believe that
the constant chemical changes, such as oxidations, or the production
of C02, or other processes, lead also to an effect which in the isolated
center can be brought about by certain salts, such as citrates or oxalates ;
namely, the setting free of Ca so that it may form dissociable colloidal
compounds and be then either replaced by Na or K, or vice versa. It
is possible that the C02 formed in the muscle may aid in this process.
The margin of a jellyfish which contains the central nervous system
contracts for a time at least, rhythmically in any solution, and certainly
in solutions of NaCl, KC1, and CaCl2. I was surprised to find that the
addition of MgCl2 to any of these solutions makes the contractions of
the margin more normal, as I believe, in an indirect way. For successful
rhythmical contractions it is necessary that a real relaxation follows the
contraction. I noticed that the edge of a Polyorchis has a tendency to
remain permanently contracted in a mixture of 100 NaCl, 2 KC1, 2 CaCl2,
and this tendency finally interfered with the contractions. This effect
is due to the Ca. I found, however, that upon the addition of MgCl2
this tendency to a continued contraction lessened and the Medusa
showed a more normal type of contractions.
If it be true that the process of stimulation consists in an exchange
of Na- and K-ions for Ca-ions (or Mg-ions?), or vice versa, in the tissues,
and that normal irritability depends upon the presence of these ions
in definite proportion in the tissues, it is to be expected that a change
in these proportions would alter the irritability and give the tissues
properties which they do not possess normally. I have already mentioned
* Loevenhart, loc. cit.
92 DYNAMICS OF LIVING MATTER
such an instance in the case of contact irritability which the muscle
assumes when put into a solution of a decalcifying salt. As an example
of abnormal sensitiveness on the part of sensory nerve endings, I may
mention an observation on the nerve endings of the skin of a decapitated
frog. If such a frog be suspended vertically over a dish containing dilute
acid or alkali, so that the feet come in contact with the acid, they will be
withdrawn. If, however, the feet be dipped into a dish of pure water,
this will not occur; but if the feet of a frog are put for half a minute
or a minute into a solution of A1C13 or Na-citrate, and are then put back
into pure water, the feet are withdrawn immediately, in a most
violent way,*- which might suggest to an anthropomorphically inclined
observer the idea that the contact with water caused the decapitated frog
the most excruciating pain. This experiment is the more surprising as
the contact with the sodium-citrate or aluminium-chloride solution does
not as a rule cause such a reaction. This hypersensitiveness of the skin
can be done away with by putting the feet subsequently into a normal
or 2 n solution of cane sugar. Urea acts similarly, but not so well.
I consider it possible that a number of cases of abnormal sensibility,
such as accompany certain neuroses, may have their basis in a change
in the proportion of metal proteids or soaplike compounds in a tissue.
As far as the action of salts on motor nerves is concerned, I have
made only the observation mentioned above, that those sodium salts
whose ions are liable to form insoluble Ca compounds are liable to cause
an increased irritability in a motor nerve. Mathews t has made a long
series of investigations on the concentration at which the various salts
produce rhythmical contractions when applied to a motor nerve. His
results practically coincide with the statements made in regard to the
muscles ; his interpretation, however, is different. From the fact
that lithium or potassium citrate causes the muscle to contract in a
rather low concentration when applied to the motor nerve, he concludes
that it is the anion which stimulates. I consider it more probable that
the citrate in this case acts on the Ca in the nerve in the way mentioned
above, and that this causes the stimulation. The formation of the Ca-
citrate is the essential feature, and this will occur no matter whether the
citrate is introduced into the muscle in the form of the sodium or lithium
salt. The nerve, however, differs from the muscle in that the former
can be stimulated through the loss of water, which is not possible in
the case of the muscle. It makes no difference whether the nerve loses
water through evaporation, or whether the water is withdrawn from the
muscle by a hypertonic solution. According to Mathews, cane sugar and
* Loeb, Pfliiger's Archiv, Vol. 91, p. 248, 1902.
t A. P. Mathews, Am. Jour. Physiology, Vol. 2, p. 455, 1904.
ELECTROLYTES IN LIVING MATTER 93
urea will bring about this effect in a — solution, while for KC1 this con-
2
centration lies at — or — . Considering the dissociation of the latter
4 5
solution, these values do not differ very widely.
I had noticed in my experiments that those salts which produce the
abnormal or increased irritability in muscles or nerves are identical
with those which are commonly used as purgatives. The action of the
purgative salts has been explained by Schmiedeberg and Cushny in
this way, that these salts inhibit the absorption of liquid from the
intestine, and the excess of fluid in the intestine causes the purgative
effect. It seemed to me that the increase in irritability caused by these
salts in the muscles and nerves of the intestine must suffice to favor an
increase in the peristaltic motions of the intestine, and that this must
cause the purgative effect. If this were correct, cathartics should be just
as effective if given subcutaneously or intravenously as if given per os ;
and moreover, it should be possible to stop these effects by giving cal-
cium salts. MacCallum* investigated this point and found indeed that
barium salts or citrates, sulphates, fluorides, etc., have cathartic effects
if injected under the skin or in the blood vessels. The quickest peristaltic
yyyt
effects could be produced by applying — solutions of these salts to the
o
peritoneal surface of the intestine. Application of a solution of CaCl2
or MgCl2 inhibited these effects. MacCallum found, in addition, that
the watery character of the stools in this case is due to an active secretion
of fluid into the intestine (and not as had been assumed to a retention
of fluid in the intestine). When he isolated an empty loop of the small
intestine in a rabbit, it was filled in a short time with a clear liquid, after
a series of drops of a sodium-citrate or barium-chloride solution had
been applied to the peritoneal surface of the intestine. It was thus
possible to obtain in a short time 20 c.c. or more of a perfectly clear
fluid from the small intestine of a small rabbit. This secretion of liquid
into the intestine could also be inhibited by CaCl2 or MgCl2.
MacCallum f showed also that the secretion of other glands can be
accelerated by the addition of the above-mentioned salts, and can be
transitorily retarded by the addition of Ca-salts. The same salts, e.g.
BaCL, or Na-citrate, which accelerate the secretion of fluid into the
intestine also accelerate the secretion through the kidneys, and this
acceleration can be counteracted by solutions of CaCl2. We have
* J. B. MacCallum, University of California Publications, Physiology, Vol. 1, p. 4, 1903;
pp. 115 and 125, 1904. Am. Jour. Physiology, Vol. X, p. 101, 1903; and p. 259, 1904.
Pfluger's Archiv, Vol. 104, 1904.
t MacCallum, University of California Publications, Physiology, Vol. I, p. 81, 1903.
94 DYNAMICS OF LIVING MATTER
already pointed out that these facts may aid us in obtaining a theory
of secretion, i.e. an understanding of the additional forces besides osmotic
pressure which must be at work in the process of secretion.
It is obvious from all these observations that the salts, especially
the Na-, K-, and Ca-salts, play a dominating role in the regulation of those
life phenomena which fall generally under the head of irritability or
stimulation and inhibition. To give a further idea of how far-reaching
the influence of salts in this direction is, I may mention the following
fact : Bock and Hoffmann * found, and other authors confirmed the fact,
that solutions of sodium salts, e.g. NaCl, NaBr, etc., when injected
into the blood, cause glycosuria in a rabbit. It seemed to me that in
this case, too, the accelerating effect of citrates and the inhibiting effect
of Ca might be found. I asked Dr. M. H. Fischer, who was then a mem-
ber' of the laboratory, to investigate this question. He found that it
is necessary in this case to infuse a NaCl solution of a higher concen-
ft
tration than — . The higher the concentration the quicker, according
to Fischer, the glycosuria ensues.f Fischer found, also, that the citrates,
etc., act more powerfully than NaCl, and that CaCl2 was, to a certain
extent, able to counteract this effect of NaCl. These observations
support the idea of PfliigerJ that this is a case of nervous glycosuria
produced through the influence of the salts upon certain nervous
elements in the medulla oblongata. It is possible that through this
influence the concentration of sugar in the blood is raised transitorily,
while the CaCl2 has the opposite effect. MacCallum § has made the
interesting observation that in this case sugar is secreted not only through
the kidney but also into the intestine.
If we finally summarize the results of these observations, we come
to the conclusion that all those phenomena which depend on the action
of muscles, nerves, or glands seem to be influenced to a large extent
by the salts, and that especially changes in the proportion of Na or K
to the Ca-ions in the tissues seem to affect their properties and their
actions. The idea to which we have given preference, namely, that
the substitution of Na or K for Ca, or vice versa, in certain organic
compounds gives rise to a contraction, may possibly have to be modified
in detail, and undoubtedly many new facts will be required and found
before we are ready for a final theory ; but I am inclined to believe that
the main structure will remain such as intimated in my papers in 1899
* Bock und Hoffmann, Reichert unci Du Bois-Reymond's Archiv, p. 550, 1871.
t Fischer, University of California Publications, Physiology, Vol. I, p. 77, 1903 ; p. 87,
1904.
\ P/luger's Archiv, Vol. 96, p. 313, 1903.
§ MacCallum, University of California Publications, Physiology, Vol. I, p. 125, 1904.
ELECTROLYTES IN LIVING MATTER 95
and 1900; namely, that the normal qualities, especially the normal
irritability, of animal tissues depend upon the presence in these tissues
of Na-, K-, Ca-, and Mg-ions in the right proportion ; that these ions are
at least partly in combination with colloids (proteids or higher fatty
acids or possibly carbohydrates), and that any sudden change in the
relative proportions of these ion lipoids or ion proteids or ion carbo-
hydrates alters the properties of the tissues and gives rise to an activity
or an inhibition of the activity, according to the sense in which the change
takes place. Finally, I believe that the natural rhythmical processes
such as heartbeat, respiration, etc., are due to a substitution of certain
metal ions for others, these substitutions being caused by the enzymatic
processes going on continually, and by which, among others, metal ions
are freed from certain combinations, and rendered available for others,
as seems to be the case in the action of rennet in the coagulation of
milk. We certainly understand by this hypothesis why the combina-
tion of the Na-, K-, Ca-, and possibly Mg-salts is so important for life
phenomena, especially those of animals.
3. The Reaction of Living Matter and the Role of Bicar-
bonates for the preservation of llfe
Not only the life of the aquatic animals but the life of every cell is
passed in a solution of electrolytes. It had generally been assumed
that the liquids in the animal tissues, as well as the sea water, had an
alkaline reaction, while the liquids of the tissues of plants had an acid
reaction. This assumption was founded upon the titration method.
Physical chemistry altered the conception of alkalinity, and measured
it by the concentration of the free hydroxyl-ions. Hober* was the first
to make use of the methods required to determine the concentration
of the hydroxyl-ions in the blood, and found with the aid of gas batteries
that the blood was slightly alkaline. His method was defective in a
detail, and later Friedenthal, f Franckel,} Farkas, and Hober himself
showed that the concentration of the hydroxyl-ions in the blood is not
higher than in distilled water. Cottrell and I found the same for sea
water. § Friedenthal showed also that the liquids of the tissues of ani-
mals and plants are practically neutral. We therefore may draw the
conclusion that life phenomena occur in a neutral liquid. The forma-
tion of C02 is one of the most general processes in living tissues. Be-
sides, other acids (e.g. lactic acid in the muscle) are formed in metabo-
* Hober, Pfliiger's Archiv, Vol. 81, p. 535, 1900.
f Friedenthal, Zeitsch. fur allgemehie Physiologie, Vol. I, p. 56, 1902.
\ Franckel, Pftiiger's Archiv, Vol. 96, p. 601, 1903.
§ Loeb, P/Ziiger's Archiv, Vol. 99, p. 637, 1903 ; and Vol. 101, p. 340, 1904.
96 DYNAMICS OF LIVING MATTER
lism. Respiration eliminates the C02 in part, but there would be
danger that every organism would finally perish through its own produc-
tion of acid were these acids not constantly neutralized. This is partly
done by the carbonates of the blood. The proteids of the blood are
also capable of neutralizing a considerable amount of acid by com-
bining with it,* and I believe this role of the proteids in the blood should
not be overlooked. The fact can be demonstrated in a striking manner
by putting a frog's muscle into ioo c.c. of ox blood, to which 10 c.c —
n IO
HC1 or 10 c.c. — NaHO have been added. The muscle does not absorb
10
water in such a solution, and remains alive for several days. If the
muscle be put into an isotonic solution of iooNaCl, 2 CaCl2, 2 KCL, to
which the same amounts of acid or alkali are added, the muscle absorbs
considerable quantities of water and dies rapidly. A third means of
keeping the reaction of the liquids of the tissues neutral is probably
the compensatory production of bases in the body, possibly induced by
the acids.
It is easy to show that marine animals are able to develop and grow
only in such solutions as are capable of neutralizing the acids which
might be formed. If the polyp be cut off from stems of Tubularia crocea,
new polyps are formed in about two days if the temperature is about
200 C. As soon as the polyp is formed, growth begins. If a solution be
prepared of 100 molecules NaCl, 2 molecules KC1, 2 molecules CaCl2,
7.8 molecules MgCl2, 3.8 molecules MgS04, isotonic with sea water,
the formation of polyps occurs more slowly than in sea water, and
growth is slight. If, however, to such a solution be added from 0.5
fit fit- ft
to 1 c.c. — NaHCO, or 0.1 c.c. — Na2C0, or 0.2 to 1.0 c.c. of a — solu-
8 J 8 ■* 10
tion of NaHO, regeneration and growth occur with normal velocity, f
These three substances have the property in common that they are
able to neutralize acids, and I am inclined to ascribe it to this peculiarity
that they are capable of accelerating growth in Tubularians. It har-
monizes with this view that NaHC03 acts better than NaHO. If,
however, a trace of acid instead of alkali is added to the original solution,
ft
growth is still more retarded. The addition of 0.1 to 0.15 c.c. — HC1
solution to 100 c.c. of the above-mentioned solution suffices to suppress
ft
growth entirely ; this corresponds to a concentration of HC1 of to
6000
* Bugarszky und Liebermann, Pfliiger's Archiv, Vol. 72, p. 51, 1898. Spiro und Pemsel,
Zeitsch. fur physiol. Chemie, Vol. 26, p. 233, 1898.
t Loeb, P/Higer's Archiv, Vol. 101, p. 340, 1904.
ELECTROLYTES IN LIVING MATTER 97
Similar conditions exist for the development of the eggs of a
1 0000
sea urchin, Arbacia. I found that in neutral solutions of NaCl, KC1,
CaCl2, MgCl2, MgS04, the eggs of Arbacia can reach the pluteus stage,
but that no normal skeletons are formed. If, however, NaHCOs is
added, normal skeletons are formed. Similar results were previously
obtained by Herbst, and in this case also the NaHC03 serves for the
neutralization of an acid. Experiments in Strongylocenlrolus furpura-
tus were still more surprising in this respect.* When these eggs were
put immediately after fertilization into a van't Hoff solution (100 NaCl,
2 KC1, 2 CaCl2, 7.8 MgCl2, 3.8 MgSOJ, only few eggs went beyond the
two-cell stage, and only very few reached the pluteus stage. If, however,
to 100 c.c. of such a solution 0.5 to 1.0 c.c. fm NaHC03 were added,
almost all the eggs went into the pluteus stage. In such a solution the
development also occurred just as fast as in normal sea water.
The addition of 0.1 c.c. f m Na2C03 solution caused also some eggs
to reach the pluteus stage. These plutei, however, did not live as long
ft
as when the bicarbonate was added. When 0.2 to 0.4 — NaHO was
10
added to 100 c.c. of the van't Hoff solution, the majority developed, but
no skeletons were formed. We must, however, take into consideration
the fact that in such solutions, as I found, NaHO is neutralized in a few
hours or in less than a day by the C02 of the air and the C02 formed
by the eggs, while the formation of a skeleton occurs only after from
forty-eight to seventy-two hours. The addition of 0.8 c.c. of a —
Na2HP04 solution acted similarly to the addition of NaHO.
I think these examples may suffice to show the importance of a
regulator which is capable of keeping the solution in which marine
animals live neutral. The same is true for the liquids in which tissues
live; this point was investigated by Rogers in experiments on the heart
of the crab. Here, also, the addition of bicarbonate made a great differ-
ence. This is also, as I believe, the explanation of the fact that Ringer's
solution is improved through the addition of a trace of NaHC03. Gaule f
was the first to point out the necessity of neutralizing the acid formed in
the heart if we wish to make it beat in an artificial solution. In fresh-
water animals, Wolfgang Ostwald made the interesting observation that,
if Gammarus be put into a salt solution of a comparatively high osmotic
pressure, life could be prolonged considerably by adding NaHC03
to the solution. He was able to show that without the addition of the
* Loeb, Pfliiger's Archiv, Vol. 103, p. 503, 1904.
t Gaule, Du Bois-Reymond''s Archiv, p. 291, 1878.
98
DYNAMICS OF LIVING MATTER
bicarbonate, the hypertonic solution was rendered acid by the
animals.*
During some of the above-mentioned experiments Osterhout and I
found that marine algse under the influence of light make the sea water
slightly alkaline, while in the dark they do not act in this way. They
produce also this alkalinity under the influence of light in a solution of
NaCl, KC1, CaCl2, which shows that the act of assimilation is accom-
panied by the excretion of a base. It is possible that this is one of the
means by which the reaction of the ocean is kept neutral in spite of the
animal life. It is also possible that this is one of the reasons why ani-
mals keep better in a well-lighted aquarium if green plants are added.
Acids as well as alkalis act as poisons in comparatively low concen-
trations. The toxic concentration for acids is generally much smaller
than for bases; the toxic effects are not altogether in proportion to the
concentration of the H- or HO- ions. Organic acids as a rule are more
toxic than should be expected from their degree of dissociation. A very
weak base like NH4OH is for Gammarus (possibly for many organisms)
more toxic than NaHO, while tetramethylammonium hydroxide is
less toxic. t This indicates that in the case of ammonia the NH3 is
responsible for the toxic effects, and not the HO- ion. This is supported
by the fact that NH4C1 is more toxic for animals than NaCl, and almost
as, if not slightly more toxic than KC1. By way of digression I may
remark that, contrary to a possibility I had considered for some time, I
have reached the conclusion that the toxic effects of electrolytes are
determined by chemical reactions and equilibrium conditions, and not by
the electric charges of the ions.
4. Electrical Stimulation
In plants, electrical stimulation plays no role, and the same may
be said to be true for those phenomena in the life of animals which they
share with plants, e.g. cell division. From all we know cell division
cannot be called forth or controlled by the galvanic current; but the
galvanic current is an excellent stimulant for the functions of those
tissues which may be considered characteristic of animals alone;
namely, muscles and nerves. It is perhaps more than a mere acci-
dent that in this respect the efficiency of Na- or K- and Ca-salts and
the electrical current coincide.
We have seen in the third lecture that the solid parts of living tissue
consist of colloids which are nonconductors, while the liquids are col-
* Wolfgang Ostwald, Pfluger's Archiv, Vol. 106, p. 568, 1905.
t Not yet published.
ELECTROLYTES IN LIVING MATTER 99
loidal solutions which contain also salts. It is obvious that such a
system can act only as a liquid conductor in which the current is carried
by the dissociated ions or such colloidal particles as possess an electric
charge. The concentration of the colloidal particles is very small
compared with that of the electrolytes in solution, so that for the con-
duction the latter are mainly or practically exclusively responsible.
When a constant current is sent through a nerve-muscle prepara-
tion or through a muscle, two kinds of effects are to be considered:
the one effect shows itself only at a rapid change in the intensity of the
current, and consists in a twitching of the muscle. The second effect
shows itself throughout the whole duration of the current, and consists
in an increase of irritability at the cathode and a decrease at the anode.
It can be shown that the twitching originates on the making of the cur-
rent at the cathode and on the breaking at the anode. The two effects
of a current are therefore different at the two poles.
When a current goes through a liquid conductor its work consists,
first, in the pulling of the ions through the liquid to the electrodes, and
second, in the withdrawal of the charges from the ions and the trans-
formation of the latter into uncharged atoms at the electrodes. The
question arises as to which of the two effects of the current the physio-
logical actions are due: to the increase of the concentrations of ions
at the electrodes, or to the withdrawal of their charges. I believe
that this question can be decided for the twitchings in favor of the idea
that the twitchings are due solely to the increase in the concentration
of the ions at one pole, and not to the loss of the charge of the ions.
It had been known for a long time that the galvanic current can
only cause a twitching in the muscle, when it goes lengthwise through
its nerve; while its effect diminishes or becomes zero when it travels
crosswise through the nerve. I .
have shown that the same is O O —
true when the nerves are stimu-
lated by induction.* Let a
and b (Fig. 16) be the elec-
trodes of a Toepler-Holtz ma-
chine, and cd the nerve of a
nerve-muscle preparation of a frog; the preparation is placed on an
insulated glass plate. If cd is parallel to the spark discharge and at
not too great a distance from it, the muscle twitches every time a spark
passes between a and b. If, however, this nerve is put at right angles
to the spark discharge and symmetrical to the two electrodes, but
equally near or even a little nearer to it than before (Fig. 17), no twitch-
* Loeb, Pfiiiger's Archiv, Vol. 67, p. 483, 1897 > anc* Vol. 69, p. 99, 1897.
IOO DYNAMICS OF LIVING MATTER
ing or a much weaker one occurs when a spark is produced. The same
effect can be produced when a Rumkorff induction apparatus is used
in place of a Toepler-Holtz machine.
The explanation of the experiment is as follows: let us assume
that at a given moment the electrode a (Fig. 16) be charged positively
and b negatively; in this case the
nerve will possess at c a negative, at
d a positive charge. As soon as the
spark passes, the charges in the nerve
will disappear also; a current will go
lengthwise through the nerve, and a
twitching will result. If, however, the
nerve is placed at right angles to the
spark discharge and symmetrical in
regard to the two electrodes (Fig. 17),
the current must go crosswise through
the nerve, and no effect or only a minimal effect ensues. In this experi-
ment no electrical charges are withdrawn from the ions, and the only
effect of the current exists in a change in the concentration of the ions
at various places in the nerve. Since, however, in this case of stimula-
tion of the nerve by induction, the effect is the same as in the case of a
direct application of the electrodes to the nerve, we must draw the con-
clusion that in the latter case also the change of concentration is suffi-
cient for the physiological effect, and that the withdrawal of the charge
from the ion cannot be the cause.
Nernst has tested the idea that the electrical current only stimu-
lates the nerve by bringing about changes in the concentration of ions
at various places in the nerves.* It had been known for some time
that the interrupted current is an excellent medium for stimulating
nerves or muscles, and it was also generally known or accepted that
alternating currents produce only weak effects when the number of
alternations becomes very high. Quantitive determinations had also
shown that the minimum intensity of an alternating current which is
required to bring about tetanus, increases with the number of alterna-
tions. These facts Nernst used as a starting point to test the idea that
the current acts only by changing the concentration of ions at the place
of stimulation. "According to our present knowledge, the galvanic
current cannot produce in a tissue, i.e. a purely electrolytic conductor,
any other effects than displacements of ions, i.e. changes of concen-
tration; we therefore conclude that the latter must be the cause of
the physiological effects. In the case of an alternating current, changes
* Nernst, Nachrichten der Geselkchaft der Wissenschaften zu Gottingen, p. 104, 1899.
ELECTROLYTES IN LIVING MATTER ioi
of concentration occur whose sense changes with the direction of the
current. When their average reaches a definite value, the physiological
effect becomes noticeable and the threshold is reached.
"It is possible to calculate the average changes of concentration
without making excessively specific assumptions. We know that in
tissues the composition of the watery solution which acts as the elec-
trolytic conductor is not everywhere the same, and especially that it
is different inside and outside the cells. Semipermeable membranes
prevent the equalization by diffusion and only at such membranes can
changes in the concentration be produced by the current. In the in-
terior of a homogenous solution, the current cannot produce such an
effect, as in each instance just as many ions migrate into such an ele-
ment of volume as leave it. At the semipermeable walls, changes of
concentration must occur, inasmuch as the current carries salts to such
a membrane which blocks their further motion. Such salts as are
able to pass through the membrane undertake the conduction of the
current through the membrane. The seat of the electrical stimulation
must therefore be at the latter.
" If a current of the density i carries the quantity v of salt to the
membrane, a migration of the salt away from the membrane must occur
through diffusion. The average change of concentration at the mem-
brane depends therefore upon the antagonistic effects of the current
and diffusion."* Nernst developed the equations for this process (ac-
cording to a method by Warburg), which show that the intensity of an
alternating current, which is just sufficient to produce a stimulating
effect, must increase in proportion to the square root of the number
of alternations in the second. Nernst tested this theory experimen-
tally in cooperation with Von Zeynek and Barratt, and found it true
for alternations from ioo to 2000. This proves that the experimental
data agree with the assumption that the electrical stimulation is due
to a change in the concentration of ions in the living tissues. Such
changes occur wherever the progress of ions is blocked, and this may
be at the limit of each individual surface film of protoplasm. In some
cases it may be at the surface of the protoplasmic layer of a cell, in
other cases, such blocks may occur inside a single cell.
Nernst's experiments were concerned only with the physiological
effects of alternating currents, and he does not discuss the effects of con-
stant currents. While a constant current is passing through a nerve
or muscle, the latter generally remains at rest. As long as the current
continues to pass through, new ions must be carried to the poles. It
is difficult to understand why this should not result in any motor effect ;
here is a gap which needs to be filled.
* Nernst und Barratt, Zeitsch filr Electrochemie, Vol. 10, p. 664, 1904.
102 DYNAMICS OF LIVING MATTER
It is of the greatest importance that the stimulation at the making
of a current occurs at the cathode, as this indicates that an increase in
the concentration of the cations is responsible for this result. On
account of the fact that the migration velocity of the potassium ions
is greater than that of the other cations in the muscle, it might appear
as though the latter were . responsible for the stimulating effect at the
cathode at the making of the current.* If the current is broken, the
stimulation occurs at the anode. It has been suggested by Griitzner
that the effect of the breaking of a current is in reality due to a current
of polarization which, of course, has the opposite direction from the
polarizing current. In this case, too, the stimulating effect at the
anode at the breaking of a current is due to an increase in the concen-
tration of the cations.
While a constant current is passing through a nerve, a region of
increased irritability exists around the cathode. I pointed out four
years ago that such a condition can be produced in the nerve by treat-
ing it with a salt which precipitates or diminishes the concentration of
the calcium ions, e.g. sodium-oxalate, -citrate, -fluoride, -carbonate,
etc. It is not impossible that a substitution of K for Ca, or vice versa, in
ion-colloids actually occurs at the cathode, while a constant current flows
through the nerve. At the anode we must expect, and we find, a de-
creased irritability. Until quite recently the phenomena of catelectrotonus
and anelectrotonus, and perhaps the effects of the current in general,
were explained on the basis of antagonistic physiological processes
being aroused by the current, one being called assimilation, the other
dissimilation. As it is impossible to connect an adequately definite
chemical idea with these terms, it is useless to discuss this view. It
is obvious that those who used these terms did so under the impression
of the since refuted notion that a metallic conduction occurs in living
tissues, and that therefore a current can directly break up chemical
compounds in the nerve or muscle ; while we now know that the disso-
ciation exists before the current starts. Moreover, the above-mentioned
experiments on the effects of induction on the nerve show that even
without any charges being withdrawn from the nerve, and without
any secondary chemical effects, the stimulation occurs. This shows
that the secondary chemical reactions at the poles, due to the trans-
formation of the ions into atoms, have nothing to do with the stimu-
lating effects of the current. I believe that for these reasons it is
advisable to discontinue the assertion that the current causes dissimi-
lation at the one and assimilation at the opposite pole of a cell.
It seems to be a general law that wherever the constant current
* I expressed this possibility in my lectures five years ago.
ELECTROLYTES IN LIVING MATTER 103
has any effect whatever, the stimulation occurs at the cathode. As
far as Infusorians are concerned, it is generally stated that the stimu-
lation occurs at the anode; but this statement is nevertheless wrong,
as Dr. Bancroft has recently shown.* If a constant current goes
through a Paramecium, the effect is that the position of the cilia on
the side of the cathode is altered, while on the side of the anode the
cilia retain their normal position, provided the current is not too strong.
The abnormal position of the cilia on the side of the cathode consists
in their free end pointing toward the oral end of the Paramecium.
It can be shown that this is the position of the cilia which is produced
by any kind of stimulus, mechanical or chemical. Budgett and I have
shown that if a Paramecium be put into — solution of NaCl (or any
salt), the Infusorian moves backward. This is due to the fact that the
salt causes a change in the position of the cilia, the latter pointing with
their free end forward instead of backward. If a constant current
is sent through a Paramecium, this change in the position of the cilia
occurs at the cathode end, while at the anode end no such change
occurs. It is therefore obvious that if we speak of the stimulating effect
of a constant current upon an Infusorian, we should state that this
stimulation occurs at the cathode side of the Infusorian. The opposite
statement is due to an observation made by Kiihne; namely, that Acti-
nospherium, sl Rhizopod, when subjected for some time to a constant
current, begins to disintegrate on the anode side.f This effect he called
a stimulation, or even tetanus. Maxwell and I, however, pointed out
long ago that this is merely a play on words, inasmuch as these phe-
nomena of disintegration (cytolysis ?) observed by Kiihne are caused
by electrolysis and are not necessarily connected with the stimulating
effect of the current. This is corroborated by observations made by
Budgett and myself 4
Not only muscular contractions but phenomena of secretion can
also be produced by a current. When a current is sent through a
trough filled with water which contains an Ambly stoma, a secretion
of whitish mucus appears on the skin wherever the outside of the
latter is struck by the current curves emanating from the anode (Figs.
18 and 19). § Here we have also apparently an anode effect of the
current. This effect depends partly, at least, upon a stimulation of the
central nervous system, and we do not know whether the stimulation
is anodic or cathodic. It may be that the influence of the central
* F. W. Bancroft, Pfliiger's Archiv, Vol, 107, p. 535, 1905.
t Kiihne, Unterstichungen itber das Protoplasma und die Contractilit'dt, Leipzig, 1864.
X Loeb und Budgett, Pfliiger's Archiv, Vol. 65, p. 518, 1879.
§ Loeb, P/iuger's Archiv, Vol. 65, p. 308, 1896.
104 DYNAMICS OF LIVING MATTER
nervous system consists only in causing a contraction of muscular or
FiG. 18. — The secretion of mucus on the skin of Amblystoma under the influence of a constant
current. The animals were kept in a trough of water through which a current passed. The
current lines were straight and parallel with the longitudinal axis of the animal. The black
dots indicate the spots where the secretion of mucus appeared. The drawing shows that the
glands secrete at the anode side of the animal where the current lines cut its surface.
contractile elements which result in the contents of the mucous glands
being squeezed out. The secretion is partly, however, a direct effect of
the current on the skin, and results finally in the
disintegration of the latter. In this case we may be
dealing with an electrolytic effect due to secondary
chemical reactions. Budgett and I found that these
anodic effects of the current on Infusorians and
Amblystoma can be imitated by applying NaHO
to these organisms. Whatever the cause of the
secretion may be, we are not justified in identifying
the disintegration of an Infusorian or the skin of
an Amblystoma with the tetanus of a muscle.
It is not our intention to give more than the
general idea of irritability and stimulation. Besides
chemical and electrical stimulation, mechanical stimu-
lation plays an important r6le. When a nerve has
been put into a decalcifying solution for some time,
or has lost water, it becomes extremely sensitive to
slight mechanical agitation. When a nerve reaches
the climax of its sensitiveness, it suffices to knock on the table that
FiG. 19.— The same
experiment as in
Fig. 18 carried out
with pieces of
Amblystoma.
ELECTROLYTES IN LIVING MATTER 105
supports the stand with the nerve to bring about a twitching of the
muscle. If we may be guided by physical analogies, — which
however, are not absolutely reliable, — this mechanical stimulation
might be compared with the effect which a mechanical agitation has,
under certain conditions, upon an oil drop on the surface of a Na2C03
solution. In this case it may lead to a dissolution of a solid soap
film on the surface, or to an alteration of the surface, by bringing new
particles of both liquid media in contact. Thus phenomena of spread-
ing may be provoked by a slight mechanical agitation. Mechanical
stimulation is much more effective in nerves than in muscles.
As a rule, heat is also mentioned as a stimulant though nobody
uses this form of energy for this purpose. The term " stimulation by
heat " is a misleading phrase, as we shall see presently.
It appears from the foregoing that by the word " stimulation " we
mean a process which is unknown to us, which, however, seems to con-
sist after the data given in this lecture in the substitution of Na- or K-
ions for Ca, or vice versa, in some colloidal (proteid or lipoid) compound
of the muscle or nerve, whereby some physical qualities of the colloidal
substances are changed.
LECTURE VI
THE EFFECTS OF HEAT AND RADIANT ENERGY UPON LIVING
MATTER
i. Effects of Heat
In discussing the effects of heat or temperature upon life phenom-
ena, we meet with the difficulty that heat influences living matter
in two ways; namely, chemically and physically. In chemical re-
gard the temperature influences the reaction velocity most powerfully,
and in physical regard it influences the viscosity of the liquids of the
cell (colloidal solutions) and their state of matter (coagulation, gela-
tion). In studying the influence of temperature upon life phenomena
we must keep these two effects apart.
There is an upper temperature limit at which all organisms can be
killed; it is generally assumed that in this case death is due to the
fact that certain proteids are coagulated by heat, and this process is not
reversible. Setchell has ascertained that in hot springs whose tem-
perature is 430 C, or above, no animals or green algae are found.*
In hot springs whose temperature is above 43 ° he found only the
CyanophycecB, whose structure is more closely related to that of the
bacteria than to that of the algae, inasmuch as they have neither
definitely differentiated nuclei nor chromophores. The highest
temperature at which CyanophycecB occurred was 630 C. Not all the
CyanophycecB were able to stand temperatures above 43 ° C, but only
a few species. The other CyanophycecB are found at a temperature
below 400 C, and were no more able to stand higher temperatures than
the real algae or animals. The CyanophycecB of the hot springs were
as a rule killed by a temperature of 73 °. From this we must con-
clude that they contain proteids whose coagulation temperature lies
above that of animals and green plants, and may be as high as 73 °.
Among the fungi many forms can resist a temperature above 43 °
or 450; the spores can generally stand a higher temperature than
the vegetative organs. Duclaux found that certain bacilli (Tyrothrix)
* W. A. Setchell, Science, N. S., Vol. 27, p. 934, 1903.
106
THE EFFECTS OF HEAT AND RADIANT ENERGY 107
found in cheese are killed in one minute at a temperature of from 8o°
to 90°; while for the spores of the same bacillus a temperature
of from 105° to 120° was required.*
Duclaux has called attention to a fact which is of importance for
the investigation of the upper temperature limit for the life of organ-
isms. According to this author it is erroneous to speak of a definite
temperature as a fatal one, instead we must speak of a deadly tem-
perature zone. This is due to the fact that the length of time which
an organism is exposed to a higher temperature is of importance. Du-
claux quotes as an example a series of experiments by Christen on the
spores of the bacilli of the soil and of hay. The spores were exposed
to a stream of steam and the time determined which was required at
the various temperatures to kill the spores.
It took at ioo°
. ,
over sixteen hours.
" " 105-no0.
. ,
two to four hours.
" " 115°
.
thirty to sixty minutes
" " 125-130°.
.
five minutes or more.
" " i35° •
.
one to five minutes.
" " 140°
>
one minute.
In warm-blooded animals 45° is generally considered a temperature
at which death occurs in a few minutes; but a temperature of 44°,
43°, or 42° is also to be considered fatal with this difference only, that
it takes a longer time to bring about death. This fact is to be con-
sidered in the treatment of fever.
It is generally held that death in these cases is due to an irreversible
heat coagulation of proteids. According to Duclaux, it can be directly
observed in microorganisms that in the fatal temperature zone the
normally homogeneous, or finely granulated, protoplasm is filled with
thick, irregularly arranged bodies, and this is the optical expression of
coagulation. The fact that the upper temperature limit differs so
widely in different forms is explained by Duclaux through differences
in the coagulation temperature of the various proteids. It is, e.g.
known that the coagulation temperature varies with the amount of
water of the colloid. According to Cramer, the mycelium of Peni-
cillium contains 87.6 water to 12.4 dry matter, while the spores have
38.9 water and 61. 1 dry substance. This may explain why the myce-
lium is killed at a lower temperature than the spores. According to
Chevreul, with an increase in the amount of water, the coagulation
temperature of albuminoids decreases. The reaction of the proto-
* Duculax, Traite de microbiologic, Vol. I, p. 2S0, 1898.
io8
DYNAMICS OF LIVING MATTER
plasm influences the temperature of coagulation, inasmuch as it is
lower when the reaction is acid, higher when the reaction is alkaline.
The experiments of Pauli show also a marked influence of salts upon
the temperature of coagulation of colloids.
The process of heat coagulation of colloids is also a function of
time. If the exposure to high temperature is not sufficiently long, only
part of the colloid coagulates; in this case an organism may again
recover. We gain from these experiments a further confirmation of the
idea expressed in an earlier lecture, that the process of coagulation or
gelation may not be a purely physical process, but the outcome of a
chemical reaction.
When we analyze the effects of heat upon life below the upper fatal
temperature zone, we must first realize that the velocity of chemical
reactions is raised to two or more times its original amount, whenever
the temperature advances io° C. (van't Hoff and Arrhenius). This
holds good for the reactions in living organisms as well as for non-
living, as may be seen from the following table concerning the influence
of temperature upon the C02 production by seeds of lupines: ioo gr.
of seeds produced in one hour according to Clausen,* the following
number of milligrams of C02 : —
Temperature
o°
5°
io°
i5°
20°
25°
3°°
35°
4o°
45°
5°°
55°
C02 PRODUCED
7.27
13.86
l8.II
34-37
43-55
58.76
85.00
100.00
115.90
104.45
46.20
17.70
We see that below the temperature of 400 the amount of C02 is approxi-
mately doubled for every rise of io° in temperature. Above this
temperature, however, the amount of C02 diminishes rapidly with any
further increase of the temperature. This is very generally observed
in enzymatic processes, and may be due to the fact that the enzyme
itself undergoes hydrolysis, which of course follows the temperature
law of van't Hoff and Arrhenius ; f or it may be that the enzyme
undergoes heat coagulation (or a process of clumping), by which
* Quoted after Cohen, Lectures on Physical Chemistry for Physicians and Biologists,
New York, 1902.
t Tammane, Zeitsch. fur physikal Chemie, Vol. 18, p. 426, 1895.
THE EFFECTS OF HEAT AND RADIANT ENERGY 109
the reaction area between enzyme and fermentable substance is
diminished. The question arises, Can we show that certain life phe-
nomena are a direct function of a reaction velocity? In my book on
the Comparative Physiology of the Brain, I expressed the idea that
the rhythmical contractions of the jellyfish, of the heart, and perhaps
in general, are a function of enzymatic processes. It seemed to me
that this idea could be put to a test, since in case it were true, the
rate of heartbeats should vary with the temperature, according to the
figures found by Arrhenius for the influence of temperature, upon re-
action velocity, i.e. we should find that with a rise of temperature of
io° C. the rate of heartbeats should at least double. At my request
Mr. Snyder undertook experiments in this direction on strips of the
ventricle of the tortoise heart. He found, indeed, that inside the tem-
perature range of from 50 to 300 C, the number of heartbeats is about
doubled for every rise of temperature of io° C. The strips of the ven-
tricle were kept in a moist chamber, which was submerged in a water
bath of constant temperature. The contractions of the strips were
recorded in the usual way. I will give as an example the records of
six experiments.* The hearts of six terrapins were put into moist
chambers, and the latter were kept at a constant temperature for two
hours and forty minutes. Two strips were kept at a temperature of
io° C, two at 200 and two at 300. The average number of heartbeats
was determined for every five or ten minutes. The left vertical column
of the following table gives the time in minutes, the other vertical
columns gives the average number of heartbeats for each heart at that
time.
Time T= io° r= 200 T= 300
Minutes Heart i Heart 2 Heart 3 Heart 4 Heart 5 Heart 6
5 9.5 9.5 2I.5 21 48 48
IO 79 21 24 48 44
15 6.7 8.7 19 18 48 40
20 7 8.2 19 16.5 41
30 7 7 10 I4
40 6.5 7.9 15.5 15.5
50 6.5 7.9 13.5 16
60 6.2 7.4 13 15
80 6.2 6.8 " 11 14-5
100 6.5 7.1 10 10
120 6.4 6.6 8 10
140 6.5 6 89
160 6.5 5.9 7.6 9
Other experiments gave similar results. The experiments show that
the influence of temperature upon the rate of contractions in different
* C. D. Snyder, University of California Publications, Physiology,', Vol. 2, p. 125, 1905.
HO DYNAMICS OF LIVING MATTER
hearts is practically the same, and that a rise of io° C. increases the
rate to a little more than twice the original figures. It was found that
temperatures above 250 C. injure the heart rather soon, and for this
reason the rate of contraction was regular at a temperature of 300 C.
for the first fifteen or twenty minutes only.
These experiments show that the heartbeat is caused by chemical
processes which go on constantly. O. Hertwig * has made experi-
ments on the influence of temperature upon the time required for the
development of the eggs of the frog. He compared the time required
to reach three successive stages in the development at the tempera-
tures of 6°, io°, 1 50, 200, and 240. The temperatures were not kept
perfectly constant. From Hertwig's results E. Cohen calculated f that
the influence of temperature followed the law of van't Hoff and
Arrhenius.
When the temperature of the protoplasm becomes sufficiently low,
e.g. approximately o° C, the velocity of the chemical reactions becomes
so small that the manifestations of life cease. Cold-blooded animals
can at any time be revived from this condition of latent life by raising
their temperature. The lack of water acts similarly to a low tempera-
ture. This is the reason why seeds can be kept alive so long. Lack
of water may reduce the reaction velocity of the hydrolytic processes
in seeds at ordinary temperature so considerably that it may become
practically zero.
The question may be raised whether lowering of the temperature
can ever kill an organism, or whether there exists a low temperature
limit for life phenomena. From our viewpoint the criterion for death
is the nonreversibility of the changes brought about by the agency
in question. We must therefore ask, Does lowering of temperature
bring about irreversible changes in the protoplasm, as does a raising of
the temperature? The answer seems to be that for many cold-blooded
animals there is no lower temperature limit in the sense of our defini-
tion, and if death occurs at a low temperature, it is due to secondary
and entirely accidental effects connected with the freezing of the water
in the cells. It is known that the formation of ice crystals in the cells
may mechanically injure and kill them. This seems to be the case in
the freezing of plants. Another accidental irreversible change is con-
nected with the thawing of animals that have been frozen. It seems
to be certain that a frog after being frozen cannot be brought back to
life again if the temperature is raised suddenly, while it may live if
allowed to thaw slowly. Barring these two secondary and mechani-
* O. Hertwig, Archiv fur Mikroskop. Anatomie und Etitwickelungsgesckichte,Vo\. 51,
p. 319, 1898. f E. Cohen, loc. cit.
THE EFFECTS OF HEAT AND RADIANT ENERGY m
cal complications, the lowering of temperature does not seem to bring
about irreversible changes in the condition of protoplasm, which are
incompatible with life. This seems to be in harmony with the fact
that living matter contains no colloidal solutions which are transformed
into irreversible gels by cooling. Gelations which are brought about
by cooling seem to be, in general, reversible processes, e.g. the gelation
of gelatine.
Experiments made recently by Pictet and others show that various
cold-blooded animals and bacteria may be cooled to very low tem-
peratures without being killed. Many, possibly most, warm-blooded
animals seem, however, to behave differently. If their blood is cooled
for some time to a temperature of 150 C. or below, they cannot again
recover. If this fact which is generally stated is correct, it shows that
in the warm-blooded animals a reversible, fatal change occurs at
such a lowering of their temperature, although we have not the slight-
est conception which substance or variable is responsible for this re-
sult. It is interesting that, according to Setchell, the Cyanophycece of
the hot springs also die when suddenly brought into water whose
temperature is below 400. It is possible that we are dealing in this
case also with some secondary effect connected with the lowering of
temperature.
The variables thus far mentioned do not yet exhaust the range of
possibilities in which temperature influences life phenomena. The
coefficient of partition of one substance between two others may vary
with the temperature. This is the case, e.g. for the coefficient of par-
tition of chloralhydrate between oil and water. This coefficient in-
creases with the temperature, which means that with an increasing
temperature more chloralhydrate will leave the watery liquids of the
body and go into the tissues which are rich in fat, e.g. nervous elements.
In consequence of this fact a frog which is poisoned with chloralhy-
drate at room temperature may become normal again upon cooling,
as chloralhydrate must in this case go from the nervous elements into
the watery liquids of the body. The following fact belongs possibly
in the same category. It is known that decapitated frogs show an
increase in irritability when kept for some time on ice. If the reaction
velocity were decisive for the reflex irritability, it should be expected
that, with an increase in temperature, the irritability would increase.
Could it be possible that in this case the coefficient of partition of some
toxic or inhibiting substance formed in the body varies in the same
sense with the temperature, as in the case of chloralhydrate? If this
were the case the fact might become intelligible that with decrease in
temperature the reflex irritability is increased.
112 DYNAMICS OF LIVING MATTER
There are, however, a number of biological effects of temperature
for which we cannot yet indicate the physical or chemical variable. It
is generally known that in many hibernating northern chrysalids the
velocity of metamorphosis is increased if the chrysalids are exposed
for some time to a temperature of o°. This fact is possibly related
to the experience, that treatment with ether can hasten the develop-
ment of buds and plants. An equally puzzling effect of heat is the
influence a low temperature has upon the production of wings in Aphides.
As long as the temperature is high and the moisture sufficient, plant
lice are wingless; but if the temperature be lowered, wings begin to
grow. In this case the lowering of temperature favors the growing of
an organ, an effect which is rather paradoxical in view of the fact that
the phenomena of development seem to be plainly a function of the
reaction velocity of underlying chemical processes.
The late Dr. Greeley * showed that a certain group of Infusorians,
Monas, can at any time be caused to form spores by exposing them for
a short time to a low and afterward to a higher temperature. Forms
of irritability can also be varied through the influence of temperature.
I have shown that positively heliotropic Copepods can be made nega-
tively heliotropic by raising the temperature, and negatively helio-
tropic Copepods can be made positively heliotropic by lowering the
temperature. This will be more fully discussed in the next lecture.
In passing I may mention that certain changes — seasonal variations —
can be brought about by changes in temperature, f
2. General Effects of Radiant Energy upon Living Matter
The electromagnetic theory of light has led to the idea that there
must exist besides the already known ether waves other waves on both
sides of the scale. Hertz discovered the method by which we can
experiment with ether waves of several centimeters or more with the
same certainty as was before possible with the shorter waves, which
are able to produce sensations of heat or light. The question had to
be put whether or not Hertzian waves had any physiological effect.
I made eight years ago an extended series of investigations on this sub-
ject, and the first experiments seemed to speak in favor of the idea that
the Hertzian waves have effects upon the nerves; but I was able to
show by a closer analysis that these apparent effects of these waves
were not due to the oscillatory character of the discharge, and that
the same results could be brought about by nonoscillatory discharges.^
* A. W. Greeley, Biological Bulletin, Vol. 3, p. 165, 1902.
t Wolfgang Ostwald, Zeitsch. fur Enhvickelungsmechanik, Vol. 18, p. 415, 1904.
j Loeb, Pfluger''s Archiv, Vol. 67, p. 483, 1897 '> and Vol. 69, p. 99, 1897.
THE EFFECTS OF HEAT AND RADIANT ENERGY 113
If we wish to study the physiological effects of ether waves, we may
therefore confine ourselves to the waves of shorter length. Among
these waves those are especially interesting for us whose length is 0.8 p
and less, inasmuch as these waves affect our retina, and produce those
chemical effects in green plants which make assimilation in these plants
possible.
Among the various known effects of these waves two are of impor-
tance for us; namely, the photochemical effect and the radiation
pressure. The latter seems to be of great importance as far as cos-
mical phenomena are concerned, as Arrhenius has shown; but I do
not believe that they play any role in life phenomena, as Radl seems
to assume,* who believes they are responsible for the heliotropic
effects of light. This view is, as I believe, contradicted by the fact
that radiation pressure is independent of the wave length, while
the heliotropic effects are eminently a function of the wave length.
This latter influences, however, the photochemical effects, and for this
reason it seems advisable to consider the possibility that the biological
effects of light are indirectly chemical effects. It seems that every
chemical reaction which is influenced by ether waves at all can be
influenced only by waves of a definite, limited period. As in this case
radiating energy is transformed into chemical energy, the light waves
can have no effect unless they are absorbed. We find indeed that in
all case's only such light waves produce a chemical or biological action
as are absorbed ; but the reverse statement, that wherever in an organ-
ism an absorption of light occurs {e.g. in pigment spots) a biological
effect must be produced, is not correct.
In order to give an idea of the possible chemical effects of light, a
few instances may be quoted. Ultraviolet rays cause the formation
of ozone from the oxygen of the air, as can be beautifully demonstrated
with the aid of the Heraeus mercury quartz lamp. According to Vogel,
violet rays cause the oxidation of guaiacum and give it a blue color,
while red rays reduce it and make it appear yellow. The oxidizing
and reducing effects of light seem to be of special physiological im-
portance. Thus Duclaux attributes the well-known sterilizing effect
of light upon bacterial cultures partly, at least, to the formation of acids
which are produced by the light in the nutritive medium. He has
shown that fats are oxidized and hydrolized under the influence of
light, and that the acid thus formed acts antiseptically. According
to the same author, sugars are oxidized in an alkaline medium by light.
Hydrogenperoxide is also found among the products formed under
the influence of light in culture media.
* Radl, Untersuchimgen iiber den Phototropismus der Tkie?'e, Leipzig, 1903.
' I
ii4
DYNAMICS OF LIVING MATTER
It is perhaps of special biological significance that the oxidation
of many dysoxidizable substances occurs more rapidly in the light than
in the dark. Schonbein and recently Jorissen have shown that alde-
hydes are oxidized more rapidly in the light than in the dark; the
same is true for oil of turpentine. According to Richardson and For-
teg, amylalcohol is oxidized quicker in light than in the dark. Bod-
lander is inclined to attribute these effects of light to a dissociation of
oxygen; his assumption is based upon the electromagnetic theory
of light.*
It is a common biological conception that the occurrence of pigment
in animals or plants bears a close relation to biological effects of light ;
we may perhaps for this reason quote an observation which bears on
this problem. The observation was made by H. W. VogeLf The
silver salts and especially the bromide of silver of common negatives
are preeminently sensitive for rays between blue and ultraviolet. If,
however, eosin or cyan in is added in traces, the maximum of the photo-
graphic effect moves toward the side of the longer waves in the spec-
trum.
After this preliminary orientation we shall discuss briefly the bio-
logical effects of light. The most important biological role of light
lies in the assimilatory activity of green plants. The transformation
of the C02 of the air into sugar (and starch) in the green plant occurs
only under the influence of light. This assimilation occurs in chloro-
phyll granules (or on their surface) inside the cells of green plants (or
certain animals). All attempts thus far made to separate a substance
from the chlorophyll which is able to form sugar from the C02 of the
air have failed.! Narcotics like ether and chloroform which inhibit
the motor activities of the cell also inhibit the chlorophyll action. (This
indicates also that the narcotics have another action than a mere physi-
cal one, as Overton assumes.) Yet it is not unlikely that in respect to
chlorophyll, a similar experience will be made to the one made in regard
to zymase; namely, that mere technical difficulties at present prevent
the isolation of the assimilating catalyzer in the chlorophyll granules
from the living cell.
The chemical side of the process of assimilation is unknown. Baeyer
suggested that from H2C03 at first formaldehyde, HCOH, is formed
which by polymerization yields C6HI206. Hoppe-Seyler § expressed
the idea that chlorophyll undergoes first a combination with H2C03
* Bodlander, Ueber langsame Verbrennung. (Ahrens' Sammlung chemiscker und
chemisch-technischer Vorlrage), Stuttgart, 1899.
t I quote after Ostwald's Grundriss der allgem. Chemie.
% R. O. Herzog, Hoppe-Seyler' s Zeitsch. fur physiol. Chemie, Vol. 35, p. 459, 1902.
§ Hoppe-Seyler, Physiologische Chemie, 1876.
THE EFFECTS OF HEAT AND RADIANT ENERGY 115
which, under the influence of light, falls apart in such a way as to yield
chlorophyll (or the catalyzer contained therein), 02, and a third prod-
uct, the latter being sugar or a substance from which sugar may be
formed. It is obvious that Hoppe-Seyler's idea represents that con-
ception of the action of the catalyzer which is more and more supported
by the facts.
The different parts of the spectrum do not accelerate the process
of assimilation equally well; chlorophyll absorbs the rays between
B and C of the spectrum, and also the rays beyond F. Engelmann
has shown by a very ingenious method that the rays between B and C
cause the most vigorous assimilation, that the effectiveness of the rays
between D and E is a minimum, and that a second maximum exists
beyond F* Those rays are therefore the most effective for the pro-
cess of assimilation which are most vigorously absorbed by the
chlorophyll.
It is as yet uncertain whether the light influences directly any other
synthetic processes than those which lead to the formation of sugars
and starch.f The lack of light must make itself felt in an indirect way
in any process in the plant for which the formation of carbohydrates
is a prerequisite, e.g. the formation of proteins.
The life of animals does not depend so directly upon the presence
of light. This is evidenced by the fact that animal life occurs in caves.
Life at the bottom of the ocean also occurs practically in the dark,
inasmuch as the light furnished by phosphorescence is only slight. It
has occasionally been stated that eggs of animals develop better or
quicker in the light than in the dark; but a closer analysis of such
statements has shown invariably, thus far, that they are due to an
experimental error. Some authors managed by faulty methods to ex-
clude the air also with the light, and others did not exclude or consider
the influence of microorganisms in their experiments. Driesch's
experiments have failed to show any influence of light upon the develop-
ment of eggs; and my own experiments in that direction have also
thus far yielded only negative results. The fact that the eggs of mam-
mals develop in the uterus, shows sufficiently that eggs can develop in
the dark.
In years of experimenting I have found only one form of animals
in which diffused daylight has an influence upon the formation of organs ;
namely, Eudendrium, a hydroid.J When stems of Eudendrium are
* Engelmann, Pfluger's Archiv, Vol. 27, p. 4S5, 1882 ; and Vol. 38, p. 386, 1886.
t As fungi can form proteids in the dark when a carbohydrate is contained in the cul-
ture medium, it seems at least possible that light is not directly required for the formation of
proteids in green plants.
I Loeb, Pfliiger's Archiv, Vol. 63, p. 273, 1895.
Il6 DYNAMICS OF LIVING MATTER
brought from the ocean to the aquarium, the old polyps die in a few
days. If the aquarium is exposed to sufficiently strong light, new polyps
are formed, while this formation does not occur in weak light or the
dark. It seems, however, as if the formation of stolons could occur
also in the dark. The different parts of the visible spectrum are not
equally effective. Behind screens of red glass the formation of polyps
was less favorable than behind screens of blue glass, even if the degree
of brightness of both kinds of glass seemed to be the same.
LECTURE VII
HELIOTROPISM
i. The Heliotropism of Sessile Organisms
Machines which are constructed artificially are arranged in such
a manner that the energy which they require is provided by the hand
of man. Through the blind play of the forces of nature durable
machines can be created only if their supply of energy is regulated
automatically. As an example of that type of machine we may men-
tion the waterfall. The waterfall is a machine which transforms dis-
tance energy into kinetic energy and heat, and the permanency of this
machine is guaranteed by the physical conditions that determine the
continued flow of water to the cataract. The green plants represent
another type of such machines ; namely, machines which, among others,
transform radiating energy into chemical energy. The permanency of
this kind of machines is guaranteed by the presence of an automatic
arrangement in such plants, whereby their stems grow toward the light.
The automatic turning of the stems of many plants toward the light is
called heliotropism. We -shall go a little deeper into the analysis of these
phenomena, inasmuch as heliotropism and similar phenomena give,
to a large extent, an insight into the mechanism of automatic self-
preservation of organisms.
The stems of many plants in the open grow vertically upward,
while the same stems when raised in a room which receives light from
only one side grow toward the window. Roots which contribute toward
the maintenance of the plant by absorbing the necessary salts from the
soil show very frequently (though not always) the opposite behavior.
When exposed to light they bend and grow away from the source of
light. This behavior is determined only by rays of a certain wave
length of the visible spectrum and possibly by some ultraviolet rays.
The dark heat rays have no such effects.
We do not yet know with the same degree of certainty, as in the case
of the process of assimilation, the relative heliotropic efficiency of each
part of the spectrum; but from experiments with colored screens it
appears that the more refractive green, blue, and violet rays of the
117
Il8 DYNAMICS OF LIVING MATTER
spectrum are more effective heliotropically than the less refractive red
and yellow rays. There exists thus apparently a division of labor,
the longer light waves accelerating assimilation, the shorter waves ac-
celerating heliotropism. This can be demonstrated with the aid of
screens, inasmuch as behind red screens the plants assimilate well,
while they do not bend or bend only slowly, toward the source of light ;
while behind a blue screen they bend actively toward the light, their
assimilation being diminished.
We call organisms which bend or grow toward the source of light
positively heliotropic or phototropic, and those that bend or grow away
from it negatively heliotropic.
As far as the mechanism of the heliotropic bending is concerned,
we must remember that in most cases it occurs most effectually in the
tips of branches or roots. As this region is also the growing region,
botanists frequently state that the process of heliotropic bending is a
function of growth. This, however, is certainly not true for grasses,
in which the bending occurs in the nodes which are flexible, while in the
less flexible internodes no bending occurs. It seems therefore as though
the phenomena of growth were not essential in the heliotropic reaction,
and that the reason that the tips react better to light than the older
parts is perhaps due in part to the fact that the latter are not so soft
and flexible.
How can light bring about heliotropic curvatures? Let us suppose
that light strikes a plant on one side only, or more strongly on one side
than on the opposite side, and that it be absorbed in the superficial
layers of tissue of that side. In this case we assume that on that side
certain chemical reactions occur with greater velocity than on the
opposite side. What these reactions are is unknown; we may think
provisionally of oxidations. This change in the velocity of chemical
reactions either produces a tendency of the soft elements on that side
to contract a little more than on the opposite side, or creates otherwise
a greater resistance to those forces which have a tendency to elongate
or stretch the plant, e.g. hydrostatic pressure inside the cells, or
imbibition of certain tissue elements. The outcome will be that one
side of the stem will be stretched more than the opposite side, and this
will bring about a curvature of the stem. Where the latter is soft at
the tip, the bending will occur only, or chiefly, in that region; and as
the degree of softness decreases rapidly from the tip downward, the
result will be that the tip will bend toward the source of light. This
result may possibly be aided by a greater photosensitiveness of the
extreme tip of the stem, although I am not aware that this is an estab-
lished fact.
HELIOTROPISM 1 19
Through the process of bending, both sides of the stem come under
the influence of light, and this fact determines the extent of the bend-
ing. As soon as the tip of the stem is bent to such an extent as to ex-
pose the symmetrical sides or elements of the stem equally to the light,
the bending must cease ; and the tip of the stem must continue to grow
in this direction. The reason for this is obviously the fact that if the
symmetrical elements of the tip are struck by the ray of light at the
same angle, the photochemical effects in symmetrical elements must
be the same, and the tendency to contract or the resistance to elonga-
tion must be the same on both sides. In this case the tip or rather its
axis of symmetry will continue to grow in the direction of the rays of
light. It is, of course, taken for granted in this discussion, that the
plant is exposed to only one source of light. What has thus far been
said refers to positively heliotropic organs, e.g. stems, which bend
toward the source of light if illuminated from one side only. The same
reasoning applies also to negatively heliotropic organs, e.g. roots, with
the difference only, that in the latter case the photochemical effects
result in a relaxation or a decreased resistance to the stretching forces
on that side of the organ where the light strikes. It appears as if there
might exist a chemical or physical difference between stem and root;
it might be possible that while the light accelerates oxidation in one
organ it accelerates reduction in the organ with opposite heliotropism.
It might also be possible that the chemical effects of light are the same
in the stem and the root of a plant, but that the colloids in the root are
affected by these substances in the opposite sense from those of the stem.
We have no data which enable us to test these suggestions.
Wortmann * has made sections through the tips of stems and roots
which were exposed to light from one side only. He found that the
cells on that side of the stem which was directed toward the light possess
denser protoplasm than the cells on the opposite side; in roots it was
the reverse. Wortmann concluded from this that the protoplasm
itself is heliotropic in the stem and that it creeps toward the illuminated
side, while in the root the reverse process takes place. Botanists have
raised the objection that a creeping of the protoplasm from cell to cell
could not occur so rapidly on account of the great resistance offered
to such a process. I wonder whether the changes which Wortmann
observed are not of a character similar to those observed by Darwin
in the basal cells of the tentacles of Drosera, an insectivorous plant,
which he designated as aggregation.! In the unstimulated condi-
tion these cells are filled with a homogeneous watery liquid of a pur-
* Wortmann, Botanische Zeihmg, 1887.
f Darwin, Insectizwrous Plants.
120 DYNAMICS OF LIVING MATTER
plish color. The walls are lined with a layer of colorless circulating
protoplasm. If, however, the cells are investigated after a prolonged
stimulation of the glands of the plant, the basal cells of the tentacle
no longer contain a homogeneous liquid, but solid masses of various
shape which have the purplish color and are surrounded with an almost
colorless liquid. These changes do not necessarily depend upon the
bending of the tentacles, but only upon the stimulation of the glands.
This process of aggregation (which may be a gelation) is reversible,
and after a period of rest the original appearance of the protoplasm
is reestablished. By way of digression we may mention that Darwin
observed that the process of aggregation traveled from the stimulated
gland to the contracting tentacle, and that what he observed here directly
may occur invisibly in the stimulated nerve fiber. It is possible that
in the positively heliotropic organs a process of aggregation occurs in
the cell on the side of the light, while in negatively heliotropic organs
the reverse occurs on the light side; and this may be the explanation
of Wortmann's observations. On the side where the protoplasm be-
comes denser (or undergoes aggregation?) the cellulose walls become
subsequently thicker than on the opposite side.
The same phenomena of heliotropism which we find in plants we
find also in sessile animals ; and the identity of the heliotropic reactions
in these two groups of organisms is so complete that it would be at
any time possible to demonstrate the phenomena and laws of plant
heliotropism in such animals, and vice versa. One of the best animal
forms in which to show this identity is Eudendrium, a hydroid. As
stated in the preceding lecture, the polyps of this hydroid soon fall off
when it is brought from the ocean into the aquarium ; but in a few days
new polyps are formed, and as soon as this occurs the little stems in
the region below the polyp bend toward the source of light, when illumi-
nated from one side only (see Figs. 20 and 21). The region in which
this curvature occurs is situated immediately below the polyps, and it
happens that in this region also the main growth of the stem occurs.
The bending of the polyp or the tip of a branch continues until the
symmetrical points of the stem are struck by light at the same angle.
If there is only one source of light this occurs when the axis of symmetry
falls into the direction of the rays of light. As soon as this happens
the stem continues to grow in the direction of the rays of light.
In Eudendrium just as in plants the more refractive blue rays are
more effective than the red rays; behind a red screen the heliotropic
curvatures in Eudendrium do not occur at all, or only slowly, while be-
hind a blue screen they occur as rapidly as in mixed daylight.
In Eudendrium we are able to convince ourselves that the region
HELIOTROPISM 1 2 1
behind the polyp in which the heliotropic curvatures occur possesses
contractility, and the forces underlying protoplasmic contraction are
responsible for the heliotropic curvature. The heliotropic curvature
consists here in the stem undergoing a stronger contraction or short-
ening on the more strongly illuminated side of the polyp than on the
opposite side. When the aquarium is turned by an angle of 1800 soon
FIGS. 20, 21.— Positive heliotropism of the polyps of Eudendrium. The new polyp-bearing stems
all grow in the direction of the rays of light which is indicated by an arrow in each figure.
(From nature.)
after the curvature occurs, the stem turns and bends in the opposite
direction* Sachs mentions that in the stems of plants also the helio-
tropic curvature can be again reversed, provided the experimenter does
not wait until the bent region of the stem has become too hard. The
heliotropic curvature in Eudendrium is therefore a phenomenon of
contractility and not a phenomenon of growth, although growth may
accidentally occur at the same time.
* These observations were made in 1895 at Woods Hole, and were mentioned briefly in
Pfliiger's Archiv, Vol. 63, p. 273, 1895.
122
DYNAMICS OF LIVING MATTER
We find heliotropic curvatures in animals where there can be no
doubt that the curvature is due solely to a process of contraction, and
not to a process of growth. Spirographis Spallanzani is a marine Anne-
lid from 10 cm. to 20 cm. long, which lives in a rather rigid yet flexible
tube. The latter is formed by a secretion from glands at the surface
of the animal. The tube is attached by the animal with its lower end
to some solid body, while the other end projects into the water. The
worm lives in the tube and only the gills, which are arranged in a spiral
at the head end of the worm, project from the tube. The gills, how-
ever, are quickly retracted, and the worm withdraws into the tube when
touched or if a shadow is cast upon it.
When such tubes with their inhabitants are put into an aquarium
which receives light from one side only, it requires, as a rule, a day or
more until the foot end of the tube is again attached to the bottom of
the aquarium. As soon as this occurs, the anterior end of the tube is
raised by the worm
until the axis of sym-
metry of the gills falls
into the direction of
the rays of light which
enter through the win-
dow into the aquarium
(Fig. 22).* When
the animal has once
reached this position it
retains it as long as
the position of the aquarium and the direction of the rays of light
remain unchanged. If, however, at any time the aquarium is turned
1800 so that the light falls in from the opposite direction, the animal
bends its tube during the next twenty-four or forty-eight hours in
such a way that the axis of symmetry of its circle of gills is again in
the direction of the rays of light (see Fig. 23). When the light
strikes the aquarium from above, the animals assume an erect
position, like the positively heliotropic stems of plants when they grow
in the open.
In these phenomena the mechanical properties of the tube play a
role. When the animal is taken out of the bent tube, the latter retains
its form. How does this permanent change of form of the tube come
about? In my opinion through new layers being secreted on the in-
side. The youngest layers of the secretion are more elastic than the
old layers, and, moreover, have at first a powerful tendency to shorten.
* Loeb, F^iiger's Archiv, Vol. 47, p. 391, 1890.
Fig. 22.-
Positive heliotropism of Spirographis Spallanzani.
(From nature.)
HELIOTROPISM
123
Fig. 23.
If such a secretion occurs on one side of the tube only, or more so than
on the opposite side, the former must become shorter than the latter,
and the result must be a curvature of the tube, that side becoming con-
cave where the new secretion has occurred.
On this assumption, which is based on many observations, the pro-
cess of heliotropic curvature is in this case as follows: when the light
strikes the circle of
gills from one side
only, in these elements
certain chemical re-
actions occur more
quickly, or to a larger
extent, than on the
opposite side. This
results in correspond-
ing alterations of the
sensory nerve endings,
the sensory nerves, and
the corresponding motor nerves, and their muscles. The sense of
these changes is such as to throw the muscles connected with the
nerves of the gills on the light side into a more powerful tonic or
static contraction than the muscles on the opposite side of the body.
The consequence is a bending of the circle of tentacles, or the head,
toward the source of light, which will continue until the axis of
symmetry of the circle of tentacles falls into the direction of the rays
of light. When this happens, symmetrical tentacles are struck at the
same angle (or in other words with equal intensity) by the rays of
light, and therefore the tone (state of contraction) of the antagonistic
muscles is the same. The result is that the circle of tentacles
becomes fixed in this position. The bending of the head produces
an increased pressure and friction of the animal against that side of
the tube which is directed toward the light, and this pressure and
friction lead to an increased secretion and the formation of a new
layer inside the tube.
Observations on another marine worm which lives in a stony tube,
Serpula uncinata (Fig. 24), add an interesting detail.* These worms
occur in colonies of thousands whose tubes are in close contact. The
tubes of this form differ from those of Spirographis in that they are
made of calcium salts (probably carbonates), and are inflexible. Never-
theless, these worms are positively heliotropic, like Spirographis, and
in the ocean all the tubes of a colony are straight and parallel, and
* Loeb, loc. cit.
124
DYNAMICS OF LIVING MATTER
directed upwards. If such a colony is put horizontally into an aqua-
rium which receives its light from above in the direction of the arrow cd,
Fig. 24, it will be observed that very soon the heads of the worms are
turned upward so that the
- iv axis of symmetry is in the
direction of the rays of light.
Very soon the tubes begin to
grow in front through the
deposition of new lime salts
(which are secreted by
glands). But the direction
of this growth is now at right
angles to the longitudinal
axis of the old tubes. This
again shows that the primary
effect of the light in the
heliotropic reactions is the
bending of the tip, or head,
of the animal through protoplasmic or muscular contraction. The bend-
ing of the tube or growth are secondary phenomena which follow the
former. I believe that the phenomena of heliotropism of sessile animals
and plants are essentially alike. The presence of nerves in animals
is no reason for denying this identity, especially since some botanists,
e.g. Hildebrandt, claim that tissues which functionally resemble nerves
also exist in plants.
FlG. 24. — Positive heliotropism of Serpula uncinata.
The light had originally struck the animal in the
direction of the arrow ab, and their tubes were
parallel with the direction of the rays. When the
light fell in the direction cd the tubes began to grow
at right angles to their former direction. Partly
diagrammatic.
2. Heliotropism or Free-moving Animals
We have seen that the essential feature of the heliotropic reaction
consists in the fact that the light automatically puts the plant or the
animal (Eudendrium, Spirographis) into such a position that the axis
of symmetry of the body, or organ, falls into the direction of the rays
of light. In the case of positively heliotropic organs, the tip, or head,
is directed toward the source of light, while it is the reverse in the case
of negatively heliotropic organs. If we imagine that such a positively
heliotropic organ, e.g. the polyp of Eudendrium, or a worm, like Spiro-
graphis, be endowed with the power of spontaneous locomotion, and
if for some internal reasons the animal were compelled to be constantly
in motion (as is the case with many pelagic larvae), we should notice
that these animals had no choice left in regard to the direction of their
motion. The light would turn them automatically until their axis of
symmetry was in the direction of the rays of light, and the animal could
HELIO TR OPISM 1 2 5
then move only in this direction. If the positively heliotropic polyp
of Eudendrium could be transformed into a free-swimming animal, it
would be compelled to swim automatically toward the source of light.
It had been known since man began to use artificial light that cer-
tain animals, especially insects, show a tendency to fly or creep to the
flame. The explanation generally given of this phenomenon was an-
thropomorphic; it was assumed that the animals fly into the flame
because they are fond of light, or that they are driven by curiosity,
or that they are afraid of the dark. It seemed to me that we had no
right to see in this tendency of animals to fly into flame the expres-
sion of an emotion, but that this might be a purely mechanical or com-
pulsory effect of the light, identical with the heliotropic curvature
observed in plants. I believed that the essential effect of the light
upon these animals might consist in a compulsory automatic turning
of the head toward the source of light, corresponding to the turning
of the head, or the tip, of a plant stem toward the light ; and that the
process of moving toward the source of light was only a secondary
phenomenon. It seemed to me also that if the stem of the plant could
suddenly acquire the power of locomotion, it would act exactly like the
animals which fly into the flame.*
I have since been able to prove directly that this deduction is cor-
rect. Eudendrium furnishes us the opportunity of observing the same
organism in rapid succession as a free-moving and as a sessile organ-
ism. In an early stage of development the larva? of Eudendrium are
ciliated pelagic organisms which swim actively. When these larvae
are in an aquarium which receives its light from one side only, they swim
at once toward that side and remain there as long as the direction of
the rays of light remains unchanged. If the aquarium is turned, they
also turn at once, and swim toward the lighted side of the aquarium.
This condition does not last long, for the larva soon attaches itself,
or rather adheres, to a solid body, and immediately afterward a polyp
grows out from the end opposite that which is attached to the solid
body. As soon as the polyp grows out, it undergoes a positively helio-
tropic curvature, as described above, provided that the light continues
to fail into the aquarium from one side only. It is thus possible to see
the same individual behave in twenty-four hours, first, like an insect
that is attracted by the light, and then like a heliotropic plant. I men-
tioned before that the heliotropic curvature of the stem of Eudendrium
occurs much more 'rapidly behind a blue than behind a red screen, if
* The first paper on the identification of the flying of animals into the light with the
heliotropic curvatures of plants appeared in January, 1S88. Sitzungsberichte der Wilrz-
bwger med. physik. Gesellsch., 1888. The same number contained also a preliminary notice
on the identity of geotropism in animals and plants.
126
DYNAMICS OF LIVING MATTER
it occurs in the latter case at all. I have found that the ciliated larvae
of Eudendrium swim rapidly toward the source of light behind a blue
screen, while they react quite slowly, or not at all, behind a red screen.*
We will now show that the same ideas also hold for forms which,
like the insects, possess a central nervous system. f We may choose
for this purpose animals like the caterpillars of Porthesia chrysorrhcsa,
or the winged Aphides. When the young caterpillars of Porthesia,
which hibernate in a nest, are brought during winter into a warm room,
they leave the nest. If a large number of these larvae are put into a
test-tube which is placed upon a table with its longitudinal axis at
right angles to the plane of the window, all the caterpillars move toward
the window side of the tube, where they remain. If the test-tube be
turned carefully by an angle of 1800 in a horizontal plane, the animals
will go back at once to the window side, and the quicker, the stronger
the intensity of the light. They react in this way, whether the source
of light is sunlight, diffused daylight, or lamplight. The representa-
tives of the anthropomorphic viewpoint would say that the animals
go to the source of light because it is brighter at the window side of the
test-tube than at the room side. It can, however, be shown
that in this case the animal has no choice, but that its head |
is turned mechanically toward the light by the latter, and
that it is compelled to move in this position. The proof
of the correctness of the mechanical, automatic, or
heliotropic view lies in the fact that the animals also
move toward the source of light, even if in so
doing they must pass from the light into the shade.
The experiment can be made in the follow-
ing simple manner: Let, through the upper
half of a window (ww, Fig. 25), direct
sunlight 5 fall upon a table, through
the lower half, the diffused daylight
(D). A test-tube ac is placed on
the table in such a way that its
long axis is at right angles with
the plane of the window; and
one half ab is in the direct
sunlight, the other half in the shade. If at the beginning of the
experiment the animals are in the direct sunlight at a, they promptly
* These observations on the larvae of Eudendrium were made in 1895 at Woods Hole,
but have not been published heretofore.
t Loeb, Der Heliotropis?nus der Thiere und seine Uebereinstimmung ??iit dem Helio-
tropismus der PJianzen, Wurzburg, 1889. Reprinted in Studies in General Physiology, Vol. I,
Chicago, 1905.
Fig. 25.
HELIOTROPISM
127
move toward the window, gathering at the window end c of the
tube, although by so doing they go from the sunshine into the
shade. This shows that the effect of light consists in turning the head
of the animal, and subsequently its whole body, toward the source of
light, so that the symmetrical points of the photosensitive surface of the
body — in this case the eyes — are struck by the rays at the same
angle. The animals will remain at the window side of the tube at
c (Fig. 25). The experiment disproves the anthropomorphic idea that
the animals go to the brightest spot in space.
It can also easily be shown that in these animals, just as in plants,
the more refrangible blue rays are more effective than the red rays, and
that the latter act like weak light. Let us suppose that a test-tube
containing the animals be placed on a table near the window
(ww, Fig. 26), through which diffused light D enters; and
that one half of the test-tube, namely, that near the
window, be covered with blue glass ah. At the beginning
of an experiment the animals are gathered at the
room end of the test-tube. They behave as if the
test-tube were entirely uncovered, and move toward
the window side of the test-tube, where they
remain. The same experiment may be repeated,
only with the difference, that the window
side ah of the test-tube is covered with
red instead of blue glass. The animals
now creep in the direction
of the window to that c^r—
point in front of a where :~r^
the light, filtered by the red
glass, begins to strike them.
Here they gather, migrat-
ing constantly in a narrow circle at the limit between red and diffused
light. The explanation of the latter experiment is as follows: As long
as the animals are at the room end of the test-tube, they are struck
simultaneously by the diffused daylight D which falls through the win-
dow, and by the weak light R which is reflected from the walls of the
room. Under these circumstances the animals are forced to turn their
heads toward the stronger source of light, namely, the window,
and consequently move toward it. As soon as they reach the point
where the light from the window has to pass through the red glass,
before striking them, the light reflected from the walls of the room,
which contains the effective blue rays, is heliotropically more effective
than the light from the window, which has lost most of its heliotropi-
FiG. 26.
128 DYNAMICS OF LIVING MATTER
cally effective rays. Consequently the heads of the animals are turned
automatically toward the room side of the test-tube, just as would be
the case with the tip of a positively heliotropic stem under similar cir-
cumstances. They move toward the room side, but cannot go far,
because, as soon as the unfiltered light from the window again strikes
them, the latter being stronger, the head is now turned automatically
toward the window again, and they move toward the latter until they
get under the red glass; and now the whole process repeats itself. It
thus happens that the animals gather in front of a at the limit between
the uncovered part of the test-tube and the red glass, where they keep
on moving in a narrow circle. Similar results are obtained if an opaque
body is substituted for the red glass.
If the whole test-tube be covered with red glass, the animals still
show a slight tendency to move toward the window side of the tube;
but their motions are no longer in a straight line as before, but more
irregular. They finally, however, gather at the window side of the
tube; but it requires much more time before they gather there than
if the test-tube is covered with blue glass. Red light acts upon these
animals like weak light; this can be shown directly by experiments
with daylight towards sunset, or in a comparatively dark room.
It seems, therefore, that these phenomena are indeed the same as
those in positively heliotropic sessile animals and plants; and we may
designate such animals whose heads are turned automatically toward
the light, when the light strikes them from one side, as positively helio-
tropic. It should be observed that the essential feature in these re-
actions is the compulsory turning of the head by the light, which leaves
the animal no choice, making all the caterpillars of Porthesia or all
the plant lice of the same culture behave exactly alike, just as in the
case of a magnet all the pieces of iron are compelled to behave alike.
This compulsory character of heliotropic reactions seems to have been
overlooked by those anthropomorphic opponents of the theory of animal
heliotropism, who offer the objection that we can turn toward the win-
dow voluntarily. This objection is about as absurd as if we should
argue against the existence of magnetism because we can turn and move
toward a magnet without being made of iron.
We not only find animals whose heads bend or turn toward the
light, which consequently must move toward the source of light, if
they move at all, but also animals whose heads bend or turn away
from the source of light. We call such animals negatively heliotropic.
Such negatively heliotropic animals are, e.g. Gammarus pulex, a fresh-
water Crustacean, the larvae of the house fly, when fully grown and
ready to go into the pupa stage, the larvae of Limulus in a certain stage,
HELIOTROPISM 1 29
Copepods and other animals, under certain conditions, as we shall
see later. For the negatively heliotropic animals the rule holds also,
that the blue rays are more effective for heliotropic reactions than the
red rays. It is easy to show that these animals move away from the
source of light in the direction of the rays of light. The fact can be
demonstrated nicely in the case of the fully grown larvae of the fly, by
compelling them to move on a table on which strong light, e.g. direct
sunlight, falls. If a shadow is thrown on the table by means of a pencil,
it will be found that the larvae move parallel with the shadow, away
from the source of light. It can also be readily demonstrated that
these animals are not, as the anthropomorphists would probably state,
afraid of the light, or fond of darkness, but they are purely negatively
heliotropic, which means that the head is bent or turned away auto-
matically by the light from the source of light, exactly like the tip of a
negatively heliotropic root. This can be shown by putting the larvae
on a table which has been placed near the window in such a position
that the half of the table which is nearer the window is struck by diffused
daylight, the other half by the direct sunlight. If the animals, at the
beginning of the experiment, are at the window side of the table in the
shade, their heads, under the influence of the light, will be mechanically
bent away from the window, and all the animals will begin to move
in the direction of the rays of light. They go from the shade into the
sunlight. I have modified this experiment by putting the larvae in
long glass tubes, one end of which lay in the shade near the window,
the other in direct sunlight. The animals went from the shade on the
room side of the tube into the end which was in the direct sunlight;
here they remained permanently, notwithstanding the fact that they
soon died from the effect of the sunlight (or the heat?). When the
animal is struck by light on one side only, those muscles which turn
the head away from the source of light contract more strongly than
their antagonists; the consequence is a bending of the head away from
the light. As soon as the symmetrical points of the photosensitive
surface of the animals are struck by the light at the same angle, the
tension of the photosensitive surface becomes equal ; hence the animals
remain in this orientation. If they move, their locomotions will there-
fore occur in the direction of the rays of light, and away from the source
of light.
We mentioned before that the laws of heliotropic curvature in plants
can be successfully demonstrated in animals. We may add that the
heliotropic motions of animals to and from the light can be demonstrated
in free-moving plants. Under certain conditions, which are not yet
completely analyzed, the cells of algae are transformed into smaller
130 DYNAMICS OF LIVING MATTER
cells, which are provided with cilia, and move out from the algae.
Strassburger showed that these swarm spores may be heliotropic and
move in the direction of the rays of light to or away from the source of
light. The blue rays are more effective in this case than the red rays.
3. The Control of the Precision and Sense of Heliotropic
Reactions in Animals
When a large number of animals are tested for heliotropic reactions,
we find that there are two problems to be solved : the first, to account
for the variations in the degree of heliotropic sensitiveness ; the second,
to account for the variation in the sense of heliotropism. As far as the
first factor is concerned, we find animals that are not heliotropic at all,
animals that show a slight degree of heliotropism, and others that are
so pronounced in their heliotropism, that their motions, and indirectly
their whole existence, is only a function of light. As far as the sense
of heliotropism is concerned, we find positively and negatively helio-
tropic animals. What causes these differences? We started with
the assumption that the heliotropic reactions are caused by a chemical
effect of light; in all such reactions time plays a role. We assume,
furthermore, that if light strikes the two sides of a symmetrical organ-
ism with unequal intensity, the velocity or the character of the chemical
reactions in the photosensitive elements of both sides of the body is
different; that in consequence of this difference the muscles, or con-
tractile elements, on one side of the organism are in a higher state of
tension than their antagonists. The consequence is a curvature or a
bending of the head. With this assumption it becomes at once obvious
what is responsible for the variation in the intensity of heliotropism.
Let us consider for the time being only positively heliotropic animals.
Some of these, e.g. winged plant lice or the caterpillars of Porthesia
(immediately after leaving the nest), may be called most intensely posi-
tively heliotropic, inasmuch as they move toward the source of light
in as straight a line as their structural imperfections permit. If they
deviate from the direction of the rays of light for only a short time,
possibly less than a second, the difference in the tension of the muscles
on both sides of the body becomes so great that it suffices to turn their
heads automatically again toward the source of light. If one side of
the body alone be exposed to the light for only a fraction of a second,
the light causes such a difference in the chemical substances formed
on both sides of the body that the threshold for the difference in the
tone of the muscles is exceeded, and the bending of the head must occur.
If, however, the light does not increase the reaction velocity as much
HELIOTROPISM 1 3 1
or if the mass of photosensitive substances is less, it will require a longer
one-sided exposure of the animal before the threshold for creating
a difference in the tension of the muscles on both sides of the body is
reached. Such animals will also move toward the source of light,
but they do not move so directly in the direction of the rays of light as
the strongly heliotropic forms, but much more irregularly. Finally, if the
light does not accelerate the reaction velocity in the animal at all, or
if the proper photosensitive substances are not present, or the proper
products are not formed in the photochemical reaction, the animal
will not appear in the slightest degree heliotropic.
The correctness of this view can, I believe, be demonstrated, by
exposing animals which in strong light are intensely positively helio-
tropic to weak light. If in the strong light they move in as straight
a line toward the source of light as the imperfections of their locomo-
tions permit, a low intensity of light can be found where they still go
toward the source of light, but where their progressive motion follows
the direction of the rays of light much less accurately. In the weaker
light the acceleration of the photochemical reactions is less than in
strong light, hence the time during which an animal can deviate from
the direction of the rays, exposing only one side of its body to the source
of light, becomes longer. The same result can be obtained by putting
these animals behind a red screen. This explains, also, the influence
of temperature upon the precision with which the heliotropic animals
follow the direction of the rays of light. Within certain limits the
precision with which such animals move in the direction of the rays
increases with the temperature.
If it be true that the immediate effect of the light in causing the
heliotropic reactions is of a chemical nature, we should expect that it
must be possible by the use of chemicals to control the precision and
sense of the heliotropic reactions. I have recently found facts * which
prove the correctness of this supposition. It may be of importance
that these chemicals are such as may be formed by the organism itself.
The experiments were made on fresh-water Crustaceans, Gammarns
pulex, Daphnia, and Cyclops. If Gammarns are left to themselves,
they may be found in any part of the aquarium clinging to solid bodies ;
but if they are disturbed by transferring them from one vessel to another,
or by merely stirring the water in the vessel in which they are, they
become, transitorily at least, negatively heliotropic. It is possible,
however, to make them at once intensely positively heliotropic, by adding
certain chemicals to the water, e.g. esters. If the negatively heliotropic
Gammarus are in a glass jar containing 50 c.c. of tap water, they become
* Loeb, University of California Publications, Physiology, Vol. 2, p. I, 1904.
132 DYNAMICS OF LIVING MATTER
positively heliotropic if i or 2 c.c. of a grammolecular solution of an
ester, e.g. ethylacetate, is added. Ethylbutyrate and methylacetate
act similarly, only they seem to be more toxic. The transformation is
rapid but not instantaneous, and by giving smaller dose? of ethylace-
tate the latent period may be prolonged.
A second means of making them positively heliotropic ir through
the addition of acids. If, instead of an ester, 1 to 2 c.c. of —
10
solution of an acid, e.g. hydrochloric, oxalic, or acetic acid, is added,
the animals also become positively heliotropic. It seems to me of im-
portance that COa is especially active in this respect. If C02 is
allowed to bubble through the vessel in which the Gammarus are, or if
from 5 to 10 c.c. of soda water (or even beer !) is added to 50 c.c. of
water, they become also positively heliotropic. Boracic acid seems to be
ineffective.
Of other substances which act in a similar way, alcohol,
paraldehyde, ammonium salts, and to a slight extent K- salts, may be
mentioned. But much higher concentrations of these substances are
needed than of the acids or esters. The positive heliotropism which
is produced in this way is only transitory.
In a colony of Cyclops some individuals, as a rule, are outspokenly
positively heliotropic, others are rather indifferent to light, and a few
may gather at the room side of a glass dish. If, however, 1 to 2 c.c.
ft
of — HC1, or another not too weak acid is added, or CO, is admitted,
10 ' 2 '
the animals all gather in a narrow region at the window side of the
vessel. If the water is rendered weakly alkaline, they become less
outspokenly positively or even, in part at least, negatively heliotropic.
I have not been able to obtain this latter effect of alkalies in Gammarus.
We see, therefore, that acid, especially C02, not only makes negatively
heliotropic Cyclops positively heliotropic, but increases the intensity
of the positive heliotropism in those that were already positive at the
beginning of the experiment.
In Daphnia it can be shown that when they are only weakly posi-
tively heliotropic, e.g. in weak light, .the addition of acid in the above-
mentioned concentration makes them intensely positively heliotropic.
I may perhaps call attention to the fact that acids, especially C02,
are formed in organisms; that, moreover, esters are formed in the
stems of many plants. It may be that these substances play a role
in the production and variation of heliotropism in plants and animals.
In my first publications on animal heliotropism I had already men-
tioned the fact that chemical changes in certain animals apparently
HELIOTROPISM 1 3 3
produce also changes in the degree and sense of heliotropism. I had
found that the caterpillars of Porthesia chrysorrhosa are outspokenly
heliotropic only as long as they are not fed. After having begun to
eat, their heliotropic sensitiveness diminishes or disappears completely ;
and in later stages of their growth and development their heliotropism
becomes very weak, even if they are caused to starve again. In ants
the intensity and the sense of heliotropism seem to be connected with
the development of their sexual products. At the time of sexual ma-
turity the males and females are markedly heliotropic ; * while in
the workers not a trace of heliotropism is demonstrable.
Many animals change the sense of heliotropism during their devel-
opment. The larvae of Limulus polyphemus are positively heliotropic
immediately after hatching, while they become negatively heliotropic
in later stages. The larvse of the common house fly are negatively
heliotropic at the end of their larval period, while this reaction neither
exists in the earlier stages nor in the imago stage. It is not impossible
that in all these cases the real cause for the changes in the sense and
intensity of heliotropism is to be found in chemical changes which
accompany sexual maturity or larval development. Larvae of Poly-
gordius (a marine Annelid) are, when caught, negatively heliotropic;
in about two hours, however, they become positively heliotropic. I
found that they could be made positively heliotropic at any time by
cooling the sea water to about 70 C, or below. It was also possible
to make positively heliotropic larvae negatively heliotropic by raising
the temperature of the water. Larvae which were positively heliotropic
at 24° were rendered negatively heliotropic by raising the temperature
to 290 C. Larvae which were positively heliotropic at room tempera-
ture became much more positively heliotropic when the temperature
was lowered; while those which were already negative at room tem-
perature remained so when the temperature was raised. f It was pos-
sible to make the same larvae in succession negative or positive at desire ;
it was only necessary not to raise the temperature too suddenly above
2 50, as this apparently injured the animals. The immediate effect
of temperature in this case was possibly a chemical one.
Results similar to those obtained by changing the temperature
could be obtained by changes in the concentration of the sea water.
When Polygordius was suddenly put into sea water diluted with fresh
water, those that were positively heliotropic before became negatively
heliotropic, while those that were already negative continued so. It
* Kellogg has observed that bees also become outspokenly positively heliotropic at the
time of their nuptial flight, Science, 1904.
t Loeb, Pfliiger's Archiv, Vol. 53, p. 81, 1893.
134 DYNAMICS OF LIVING MATTER
sufficed for this purpose to add from 30 to 60 c.c. of fresh water to 100
c.c. of sea water. If, however, the concentration of the sea water was
raised through the addition of 1 gr. NaCl, or the equivalent amount
of some other salt, or of sugar, the animals became positively helio-
tropic. Loss of water on the part of the animal acted therefore like cool-
ing, and an increase in the amount of water like raising the temperature.
I made similar observations concerning the changes in the sense
of heliotropism in Copepods.
In some forms light itself seems to play a role in the sense of helio-
tropism. The Nauplii of Balanus are positively heliotropic upon
leaving the egg, but they soon become negatively heliotropic. Groom
and I found that when the larvae were kept in a dark room which was
illuminated by a gas flame, they remained positively heliotropic toward
the flame. In strong light they soon became negatively heliotropic,
and, as a rule, the quicker the stronger the light.* These experiments
were made at Naples. Experiments which I made on Nauplii of
Balanus in Berkeley showed that the reaction of these latter toward
light differs somewhat from those found at Naples, and is much more
complicated.
While in all these cases one would naturally suspect that chemical
influences determine the sense and precision of heliotropic reactions
of animals, the same is not so obvious in the following cases. Miss
Towle found that Cypridopsis, an Ostracode, is at times negatively,
at other times positively, heliotropic. The artificial transformation of
positively heliotropic specimens into negatively heliotropic was not pos-
sible. It was, however, possible to make negatively heliotropic speci-
mens positively heliotropic by mechanical agitation. f S. J. Holmes
observed that terrestrial Amphipods are positively heliotropic, while
the Amphipods living in the water are negatively heliotropic. This
led him to try whether or not terrestrial Amphipods would become
negatively heliotropic when thrown into water. He found, indeed, that
one of these terrestrial Amphipods, Orchestia, when thrown into the
water, becomes rapidly negatively heliotropic. In sea water these
animals remain permanently negatively heliotropic, while in fresh
water they become positively heliotropic again before they die.J
I have often wondered whether there are any differences in the be-
havior of negatively and positively heliotropic animals aside from their
behavior toward light. When larvae of Polygordius were kept in a ver-
tical test-tube in a dark room, it often happened that one lot of these
* Groom and Loeb, Biologisches Centralblatt, Vol. IO, p. 1 69, 1 890.
f E. W. Towle, Am. Jour. Physiology, Vol. 3, p. 345, 1900.
% S. J. Holmes, Am. Jour. Physiology, Vol. 5, p. 21 1, 1901.
HELIOTROPISM 1 3 5
animals collected at the top, another at the bottom of the tube. When
these two groups were separated in two different vessels and exposed
to the light, it was found that those animals that had collected at the
bottom of the tube in the dark room were invariably negatively helio-
tropic, while the others were positively heliotropic. The reverse was
also true; namely, that if positively and negatively heliotropic larvae
of Polygoriiius were put into vertical tubes in the dark, the positively
heliotropic specimens invariably gathered at the top, the others at the
bottom of the tube. In Limulus larvae I noticed that when positively
heliotropic they swam at the surface of the dish, while in the negatively
heliotropic state they crept at the bottom. It is, however, questionable
how far this observation can be generalized. In the Nauplii of Bala-
nns I have noticed that negatively heliotropic larvae swim with the
same velocity toward the room side as positively heliotropic animals
move in the opposite direction.
Heliotropism, and especially positive heliotropism, is extremely
common among animals, particularly pelagic animals. I have found
pelagic larvae of fish which reacted in just as machinelike a manner
to light as caterpillars or Crustaceans ; but in adult fish, and particularly
in higher vertebrates, typical heliotropic reactions can no longer be
demonstrated. It rarely happens that animals endowed with the
mechanisms of associative memory react in such a machinelike manner
to the elementary forces of nature as the heliotropic animals which
we have discussed.
Heliotropism plays a wide role in determining the behavior of
animals, and there are animals whose life becomes at certain periods
of their existence, at least, a function of light. Since I have treated
the bearing of heliotropism upon the theory of animal instincts in
another place * it need not be repeated here.
4. The Reaction of Animals to Sudden Changes in the Inten-
sity of Light
One source of endless misunderstandings and waste of time among
scientists results from the indiscriminate application of one principle
to all those cases which by accident have one feature in common with
the cases covered by the principle, but differ in almost every other re-
gard. We have already mentioned the absurdity of the idea that every
kind of turning to the light should be a case of heliotropism. Helio-
tropism covers only those cases where the turning to the light is com-
* Loeb, Comparative Physiology of the Brain and Comparative Psychology, G. P. Put-
nam's Sons.
136 DYNAMICS OF LIVING MATTER
pulsory and irresistible, and is brought about automatically or mechani-
cally by the light itself. On the other hand, there are compulsory and
mechanical reactions to light which are not cases of heliotropism;
namely, the reaction to sudden changes in the intensity of light. When
the Serpula stretch out their gills, they instantly withdraw them if an
opaque body passes between the animal and the source of light. Spiro-
graphs behaves similarly. Instead of casting a shadow upon the
animal, the same reaction may be produced by suddenly closing the
shutters of the windows. It is thus evident that we are dealing here
with the effect of a sudden decrease in the intensity of light compara-
ble to the twitching of a muscle upon the breaking or sudden decrease
in the intensity of a current. It should be noticed, however, that I
never succeeded in bringing about the sudden contraction of Serpula
or Spirographis by a sudden increase in the intensity of light.
There are other forms which react as well upon a sudden increase as
upon a sudden decrease in the intensity of light, e.g. fresh-water Plana-
rians and earthworms. In these forms a sudden increase in the in-
tensity of light causes restlessness, while the reverse change causes the
animals to come to rest. This may lead to the gathering of the animals
in such parts of the vessel as represent relative minima in the intensity
of illumination. When such an animal comes from a bright spot to
a darker spot, it comes to rest ("falls asleep"). In consequence of
this fact such a relative minimum must act like a trap in which the
animals are caught. The consequence is that the number of animals
collecting in such a place must always increase, inasmuch as any ani-
mal which gets to such a spot by chance must remain there because its
motions cease.
The fact that we are dealing here with the gathering of animals
caused by light might easily mislead an investigator to mistake these
reactions for negative heliotropism. It was a long time before I real-
ized myself that I was dealing here with an effect of light which was
specifically different from heliotropism. In the latter case the results
are a function of the constant intensity, in the former a function of the
quotient of the change of intensity over time. It is, however, easy to
demonstrate the difference between the two kinds of gathering, experi-
mentally. If negatively heliotropic animals be put into a cylindrical
glass jar, and it be placed near a source of light, the animals move in the
direction of the rays gathering at the negative end of the jar (b, Fig. 27).
If fresh- water Planarians are put into such a circular glass dish, they show
very little or no tendency to move in the direction of the rays of light,
creeping along in an irregular manner and gathering not at the nega-
tive or positive side of the jar, but on both sides, c and d (Fig. 27),
HELIO TR OPISM 1 3 7
where, on account of the refraction of light, the intensity is a relative
minimum.*
The fact can be demonstrated still differently: if one part of the
aquarium is covered with an opaque body, these organisms gradually
gather under the covered part, where they come
to rest. If the cover is suddenly removed, they w w
begin to become restless and creep about. In
heliotropism we deal with an automatic orientation
of the animal by light, which compels all the
animals to move in the same direction. In
animals like earthworms or Planarians this
orienting effect of light is very slight, and the
animals may or do move in every direction.
Of course, it is possible that sensitiveness to
sudden changes in the intensity of light exists
also in a heliotropic animal. Serpula uncinata
is positively heliotropic, and yet contracts rapidly when the inten-
sity of the light is suddenly decreased. In Planarians the sensitive-
ness to changes in intensity prevails, while, according to G. H. Parker,
they show a slight degree of negative heliotropism.
* Loeb, Pfliiger's Archiv, Vol. 53, p. 81, 1893.
LECTURE VIII
FURTHER FACTS CONCERNING TROPISMS AND RELATED
PHENOMENA
i. General Theory oe Tropisms *
In the preceding lecture and in my former writings I had given a
theory of tropisms which may be considered as an application of Fara-
day's conception of lines of force. We may conceive space as being
traversed by various kinds of lines of force, some of which are present
permanently, and in the same direction, e.g. lines of gravitation; while
others may be present or absent, and may vary their direction, e.g.
light rays, or electrical lines of force, etc. The bodies of living organ-
isms possess as a rule a symmetrical structure, not only morphologically
but also chemically, or dynamically. By this I mean that symmetrical
points at the surface of the body of an organism possess practically
the same chemical substances qualitatively as well as quantitatively,
and hence the velocity and kind of chemical reactions must be the same
for such symmetrical points. Asymmetrical points of the organism,
however, possess a different chemical structure, and hence the velocity
and kind of reaction does not need to be, and probably generally is
not, the same.
It is presumed, and is in all probability true, that those forms of
energy which influence orientation or the direction of the motion of
an organism, do so because they alter the velocity or the character
of the reaction.
On account of the symmetrical structure the organisms are oriented
automatically in any field of force which affects their chemical reactions
neither too little nor too much, in such a way, that symmetrical points
of the surface of the body are struck by the current curves at the same
angle. In this case each element of the surface receives the same num-
ber of current curves.
The way in which this automatic orientation of the organism is
brought about has already been mentioned in a preceding lecture. If
* Cf. Loeb, Pfliiger's Archiv, Vol. 64, p. 439, 1897.
138
TROPISMS AND RELATED PHENOMENA 139
the current curves of radiating energy, e.g. light rays, strike an animal
on one side only, or on one side more strongly than on the symmetrical
side, the velocity or the kind of chemical reactions in the symmetrical
photosensitive points of both sides of the body will be different. The
consequence will be in a positively heliotropic animal a stronger ten-
sion or tendency to contract in the muscles connected with the photo-
sensitive points of the one side of the body than in those connected
with the opposite side. It seems that in animals the region at the oral
pole is, as a rule, more sensitive than the rest of the body. Consequently
the tension of the muscles determining the position of the head or oral
pole is more intensely affected by differences in the intensity of light
than that of the muscles of the rest of the body. The head is conse-
quently bent until its symmetrical photosensitive points are again
struck at the same angle by the rays of light. The tension of the sym-
metrical muscles of the head then again becomes equal, and the head
must remain in this position unless other forces disturb its orientation.
The rest of the body follows the orientation of the head, a point which
is more fully discussed in my book on Brain Physiology.
Aside from the data given in the previous lecture on this subject,
two more facts support this view. The one-sided section or destruc-
tion of certain parts of the brain causes a diminution in tone in the
muscles which turn the body toward one side. The consequence is
that animals in which such an operation has been performed, no longer,
or only with difficulty, are able to move in a straight line, moving instead
constantly in a circle or spiral.* We speak in such cases of forced
movements. The same condition which is brought about in a more
permanent way by certain one-sided lesions of the brain can be pro-
duced transitorily by a one-sided illumination of the photosensitive
surface of a highly heliotropic animal, with this difference only, that
the very difference in the tension of the muscles and the forced move-
ment resulting therefrom leads to a remedy of the evil by bringing the
symmetrical points of the animal back into a position where they are
struck at the same angle by the lines of force.
The second fact in support of this conception is that when the photo-
sensitive elements on one side of the body are eliminated, the animal is
compelled to move in a circle. S. J. Holmes f and Parker 1 have
indeed found that such is the case. I will quote Parker's observation
on the subject. His experiments were made on a butterfly (Vanessa
* Loeb, Comparative Physiology of the Brain, p. 150.
t S. J. Holmes, Am. Jour. Physiology, Vol. 5, p. 211, 1901.
J G. H. Parker, The Phototropism of the Mourning-cloak Butterfly {Vanessa Antiopa),
Mark Anniversary Volume, 1903.
140 DYNAMICS OF LIVING MATTER
antiopa). "Since the head is the portion stimulated by light, it is
natural to suspect that the eyes are the particular parts concerned. Loeb
has pointed out that the orientation of an organism in light is depend-
ent upon the equal stimulation of symmetrical points on its body.
Should the eyes be the parts stimulated, any interference with one of
these ought to result in a disturbance of the direction of the butterfly's
locomotion. Thus if the cornea of one eye were blackened, the insect
in locomotion, being positively phototropic, ought to move as though
that eye were in shade; namely, in a circle, with the unaffected eye
toward the center. Specimens prepared by blacking the cornea of one
eye showed the expected response. When the right eye was covered,
the insects crept or flew in a circle, with the left side invariably toward
the center; and the reverse took place when the other eye alone was
blackened. These circus movements agree with those observed by
Holmes in other positively phototropic Arthropods." These data ex-
plain why in a field of force which affects the chemical processes in an
animal neither too little nor too much, the animal is turned automati-
cally until symmetrical points of its surface are struck equally by the
lines of force. As soon as this occurs the animals must keep this
orientation, and therefore have no further choice in the direction of
their motions.
Whether the oral pole is turned toward the source of the lines of
force or away from it, depends upon whether the energy which streams
along the lines of force alters the chemical reactions in such a way
as to increase the tone of the muscles (or the contractile protoplasm)
connected with the stimulated elements, or to decrease it.
The light rays are not the only lines of force which bring about an
automatic orientation of animals; the galvanic current curves act as
lines of force, and we speak in that case of galvanotropic orientation,
or galvanotropism. A number of plants and animals are oriented
automatically by the lines of gravitation emanating from the center
of the earth, and are compelled to put their axes or planes of symmetry
into a vertical direction (geotropism). While in these cases the current
curves are very marked, the same cannot be said in regard to the lines
of force in a field of diffusion. The lines of diffusion determined by the
particles emanating from a center of diffusion should be straight lines,
but in reality currents of air or liquids cause disturbances of these
ideal lines. It thus happens that in the case of chemotropism we can
at the best expect only an approximate orientation.
There are some other tropismlike reactions of animals and plants
which we shall discuss here, although they do not strictly belong in this
chapter; namely, stereotropism and rheotropism.
.,
TROPISMS AND RELATED PHENOMENA
141
2. Galvanotropism
When animals are exposed to a galvanic current, compulsory re-
actions may occur which agree with the compulsory reactions produced
by light, with the difference that we have to substitute the current
curves for the light rays. When parallel current curves strike a sym-
metrical organ or organism sidewise, the contractile elements, e.g.
muscles, on one side of the organ, or organism, undergo a higher degree
of tension than on the other side; the outcome is a bending or turning
of the organ or animal until its axis, or plane of symmetry, is in the
direction of the current curves. As soon as this occurs, the symmet-
rical elements of the surface of the body are struck at the same angle
by the current curves and the kind and acceleration of chemical re-
action is the same on both sides of the organism; consequently the
symmetrical muscle elements show the same state of contraction. But
the fact that the current curves penetrate throughout the whole animal
causes often complications which prevent an ideal orientation such as
we observe in the case of light.
A most striking case of galvanotropism was found recently by Ban-
croft * in Poly orchis penicillata, a Medusa. "The method of experi-
mentation consisted in cutting the Medusa in various ways, and placing
the pieces in a trough of sea water through which the galvanic current
was conducted with non-polarizable electrodes. The current strength
varied from 25 to 200S. The responses were usually distinct with
25S, but became more decided as the current was increased.
"If a meridional strip (Fig. 28) passing from the edge on one side
through the center of the bell to the other edge be prepared and the
current passed through transversely, tenta-
cles and manubrium turn and point toward
the cathode (Fig. 28). A reversal of the
current initiates a turning of these organs
in the opposite direction, which is usually
completed in a few seconds. This can be
repeated many times and the tentacles
continue to respond after hours of activity.
The manubrium, however, tires sooner and
fails to respond. If the strip is placed
with its subumbrella surface upward and extended in a straight line
parallel to the current lines (Fig. 29), the making of the current
causes the tentacles at the anode end to turn through an angle of
* F. W. Bancroft, Jour. Exper. Zool., Vol. I, p. 289, 1904.
+
Fig. 28. — After Bancroft.
142 DYNAMICS OF LIVING MATTER
i8o° and point toward the cathode. The tentacles at the cathode
end become more crowded together, reminding one of the tip of a
moistened paint brush, and also point more directly toward the cathode.
The experiment may be varied in still other ways by cutting smaller
or larger pieces from the edge of the swimming bell, but the response
is always the same.
■ — ^_s^i — — "Ife, The tentacles, wher-
J&^&, JB? ever possible, and to
Fig. 29.— After Bancroft. a *ess extent the
manubrium, bend so
as to point toward the cathode. The response depends in no way
upon the connection of these organs with the swimming bell, muscles,
or nerve ring, for it is obtained equally well with isolated tentacles
and pieces of tentacles. Isolated tentacles when placed transversely
to the current lines curve so as to assume a more or less complete
U -shape, with their concave side toward the cathode. When placed
parallel to the current, the tentacles do not curve" (Fig. 30). The
latter observation shows very nicely the fact that the whole reaction
is due merely to an increase in the tension of the muscles on the
cathode side of the organ.
We are dealing here with the galvanotropic reactions of sessile
organs where the whole reaction is merely a galvanotropic curvature.
Wherever the current affects
the locomotive organs of a free-
swimming animal, besides the
galvanotropic orientation of the
animal, a swimming either
toward the cathode or anode
must occur. As an example,
the reaction of an Infusorian,
Paramecium, may be quoted.
Verworn observed that Para-
mecium, when put into a trough
through which a galvanic cur-
rent passes, is oriented in such fig. 30.— after Bancroft.
a way as to put its oral pole
toward the cathode. It swims in this orientation toward the cathode.*
The mechanism of this reaction was discovered by Ludloff.f The
locomotion of Paramecium is brought about by cilia. As a rule,
these cilia are directed backward (A, Fig. 31), and therefore their
* Verworn, Pflilger's Archiv, Vol. 45, p. I ; and Vol. 46, p. 267, 1889.
t Ludloff, Pflilger's Archiv, Vol. 59, p. 525, 1895.
TROPISMS AND RELATED PHENOMENA
H3
A
powerful stroke being directed backward, the animal is pushed
forward. Ludloff found that if a Paramecium is struck sidewise
by the current, the position of the cilia on the cathode side is re-
versed; namely, they are now turned forward (Fig. 31, B); while
on the anode side of the animal they remain practically unaltered.
Instead of striking symmetrically on both sides of the animal, the cilia
on the cathode side strike forward powerfully, those on
the anode side backward. The animal is thus under the
influence of a couple of forces which turn its oral pole
toward the cathode side. As soon as it is in this condition
the symmetrical cilia are struck equally by the current
curves, and they must assume a symmetrical position.
Such is, indeed, the case. They are now pointed forward
at the oral end, at the aboral end backward (B, Fig. 31).
As long as the current is not too strong, the oral region
where the cilia point forward is rather small, and therefore
the cilia which are pointed backward prevail, and the
organism moves forward toward the cathode. That the
motion of the organism to the cathode is exclusively due to
the position of the cilia, and not to a stimulating effect
B +
-B
^^^^p^r
Fig. 31. — After Bancroft.
A. Normal position of the cilia in a Paramcecium.
B. Forced position of the cilia when the Paratncsciut?t is in a trough through
which a constant galvanic current flows. The free ends of the cilia on the
cathode side of the organism point in this case toward its oral pole.
of the current at the anode, as Verworn had assumed, follows from
observations made by Budgett and myself.* We found that in certain
solutions, e.g. 0.8 per cent NaCl solution, the Paramcecia show a
tendency to swim backward. When exposed to a galvanic current
in such a solution, they show a tendency to go to the anode. The
explanation is that in such an organism the cilia are pointed forward
under the influence of the solution. Bancroft found that when the
current goes crosswise through such a Paramecium, the cilia on the
cathode side continue to point forward while those on the anode side
assume their natural position, pointing backward. The animal is
thus turned with its oral pole toward the cathode. As soon as this
Loeb and Budgett, PJliiger's Archiv, Vol. 65, p. 518, 1897.
144 DYNAMICS OF LIVING MATTER
occurs the cilia on both sides of the body, with the exception of a
small number on the anode side, point forward, and the animal is
therefore pushed backward to the anode.
Maxwell and I have investigated a little more carefully the reactions
of a Crustacean, Palcemonetes, to a constant current.* When these
animals are put into a trough through which a current passes (whose
intensity is neither too weak nor too strong), all the animals move
gradually toward the anode. The Crustacean can swim forward
or backward and can walk forward, sidewise, or backward. The
effect of the current does not in this case consist in a compulsory orien-
tation of the organism, but merely in a compulsory change in the rela-
tive position of the legs, or swimmerets. The result is always such as
to facilitate the motion to the anode, and to render more difficult the
locomotion to the cathode. "Palcemonetes uses the third, fourth, and
fifth pairs of legs for its locomotion. The third pair pulls in the for-
ward movement, and the fifth pair pushes. The fourth pair generally
acts like the fifth, and requires no further attention. If a current be
sent through the animal longitudinally, from head to tail, and the
strength be increased gradually, a change soon takes place in the posi-
tion of the legs. In the third pair the tension of the flexors predomi-
nates, in the fifth the tension of the extensors. The animal can
thus move easily with the pulling of the third and the pushing of the
fifth pairs of legs, that is to say, the current changes the tension of
the muscles in such a way that the forward motion is rendered easy, the
backward difficult. Hence it can easily go toward the anode, but only
with difficulty toward the cathode. If a current be sent through the
animal in the opposite direction, namely, from tail to head, the
third pair of legs is extended, the fifth pair bent; that is, the third pair
can push, and the fifth pair pull. The animal will thus go backward
easily and forward with difficulty. When Palcemonetes swims for-
ward, the swimming appendages, among which the tail fin must be
counted, push backward forcibly and forward gently; in swimming
backward the opposite occurs. If the current be sent through Palce-
monetes in the direction from head to tail, the" swimming appendages
and the tail also are stretched backward, or dorsad, to their fullest
extent. This proves that the tension of the muscles that move those
organs backward is greater than that of their antagonists. The shrimp
can thus swim forward toward the anode easily under the influence
of such a current, but backward only with difficulty. If the current
passes through in the opposite direction, from tail to head, the tail and
the ventral appendages are turned forward. The tension and the
* Loeb and Maxwell, Pfliiger's Archiv, Vol. 63, 1896.
TROPISMS AND RELATED PHENOMENA 145
development of energy now predominate in those muscles which move
the swimming appendages forward. In this way the animal can
swim backward easily, while it is difficult or impossible for it to swim
forward.
" Palamonetes can also walk sidewise. This movement is pro-
duced by the pulling of the legs on the side toward which the animal
is moving (contraction of the flexors), while the legs of the other side
push (contraction of the extensors). If a current be sent transversely,
say from right to left, through the animal, the legs of the right side
assume the flexor position, those of the left side the extensor position.
The transverse current assists the animal in moving toward the right,
toward the anode, and prevents it from moving toward the left, toward
the cathode." *
The galvanotropic reactions were first discovered in vertebrates.
Purkinje noticed that if a galvanic current is sent through the brain
of a human being, sensations of motion and dizziness are produced.
Brenner recognized the polar character of this effect, and found that
if a current of sufficient intensity is sent laterally through the head,
the person falls toward the anode side upon making the current, toward
the cathode side, upon breaking the current. # Mach noticed that if a
current is sent sidewise through fishes, the animals have a tendency
to roll toward the anode side.f
The introduction of the term "galvanotropism" into physiology dates
from J. Miiller-Hettlingen, who found in Hermann's laboratory that
if the seedlings of Vicia faba are exposed to a constant current, the tips
of the roots bend toward the cathode. $ Hermann soon afterward
made similar experiments on the larvae of frogs. He found that these
animals, when put into a trough through which a current goes, are turned
into the direction of the current curves, putting their heads toward the
anode. § I must, however, admit that I never succeeded in repeating
this experiment on tadpoles.
Blasius and Schweizer|| found that a large number of animals, when
put into a trough with water through which a constant current goes,
have a tendency to go to the anode. They assume that the current
acting upon the central nervous system causes sensations of pain when
it goes in the ascending direction through the animal; while it calms
the animal when it goes in the opposite direction (from head to tail).
* Quoted from Loeb, Comparative Physiology of the Brain and Comparative Psychology,
New York, 1900.
t Mach, Grundlinien der T.ehre von den Bewegungsempfindnngen, Leipzig, 1S75.
% T. Miiller-Hettlingen, Pfliiger's Archiv, Vol. 31, p. 193, 1883.
§ Hermann, Pfliiger's Archiv, Vol. 37, p. 457, 1885 ; and Vol. 39, p. 414, 1886.
|| Blasius und Schweizer, Pfliiger's Archiv, Vol. 53, p. 493, 1893.
L
146 DYNAMICS OF LIVING MATTER
The animals according to these authors choose the position which oc-
casions the least pain; namely, with their heads toward the anode.
This assumption is contradicted by the above-mentioned experiences
on the effects of the galvanic current on the brain of human beings,
which show that the tendency to fall toward one side is not produced,
and not even accompanied, by any sensation of pain. Moreover, the
above-mentioned observation on the effects of the current on the ten-
tacles of Polyorchism the reactions of Paramacium, and the observations
on Palcemonetes, show that these reactions find their adequate explana-
tion in the direct effects of the current upon the organs or nervous
mechanism of locomotion; that there is no room left for the smuggling
in of hypothetical pain sensations between the current and its effect
upon the mechanism of locomotion. I have repeatedly pointed out
that it is superfluous, and often in direct contradiction to the facts,
to assume the existence of human sensations in lower animals, and to
put these hypothetical sensations as a necessary link between the ex-
ternal stimulus and its motor effect. It is easy to see what led Blasius
and Schweizer to their assumption. If we send a current through a
trough in which are found specimens of a Salamander, Ambly stoma,
the attitude of the animal changes considerably, according to the direc-
tion in which the current goes. When the current goes from tail to
head, the animal assumes an opisthotonic position, with its mouth
open. It is evidently this condition, together with a certain restless-
ness, which caused Blasius and Schweizer to assume that the ascend-
ing current excites the animal painfully. If we, however, look at the
condition of the animal when the current goes from head to tail, we see
that in this case the animal is also in a forced position; namely, with
its head downward and its back convex. The right expression of
the facts is, it seems to me, that the descending as well as the ascending
current change the tension of certain muscles; but while the latter
causes the contraction of the extensors of the vertebral column and of
correlated muscles, the former causes the contraction of the flexors.
The assumption of the pain sensation as the necessary link in the one
case and not in the other is quite arbitrary and unnecessary. It is
probable that in animals possessing a central nervous system, the
galvanotropic reactions are brought about chiefly by the action of the
current upon the central nervous system. Since the galvanic current
influences not only the superficial layers of an organism like the light,
but penetrates through the whole body, the cases of ideal galvanotropic
orientation are not so common as those of heliotropic orientation.
TROPISMS AND RELATED PHENOMENA
147
Geotropism
It is well known that even in the dark the tips of the main roots of
many plants show a tendency to grow vertically downward, while the
tips of the main stem show the opposite tendency. If such plants
are put into a position other than vertical, the tip bends until the
vertical lines strike symmetrical points at the same angle. In such
cases we call the roots positively, the stems negatively, geotropic.
Knight has shown by putting plants on a rotating disk that these effects
are due to gravitation. In a centrifugal machine the tips of the root
grow toward the periphery, the stems toward the center of the disk.
In grasses the curvature occurs in the nodes, while in other forms it
occurs in the growing region near the tip of the root or the stem.
While chemistry furnishes sufficient data for the assumption of
photochemical effects in organisms, we do not know of any direct effect
of gravitation upon chemical reactions. Eight years ago I pointed out
that such an effect might occur in this way ; namely, that in the cells,
or in certain cells, of geotropic organs, nonmiscible substances (e.g.
solids and liquids) might exist, and that by the change in the position
of the organ a change in the relative position of these phases might
be brought about.* This change in position might
be connected with an acceleration of the reactions on
the one side, and the reverse effect on the opposite
side of the organ. I was led to such an assumption
by the observations made on the resting muscle in a
stretched and normal condition. If the excised muscle
of a frog is stretched passively by a weight, it produces
more lactic acid than in the unstretched condition-!
I am inclined to attribute this effect of the stretching
merely to a change in the form of the muscle. It
might be possible that the stretching increases the
surface of certain (the anisotropic?) elements in the
muscle, whereby the area of contact (with the isotropic
substance?) and therefore the reaction velocity might
be increased. Something similar might happen in
geotropic organs, when they are put into a hori-
zontal position. Suppose that in the normal , (upright) condition of
the stem certain solid or viscous substances (e.g. nuclei) of a higher
specific gravity than the other constituents of the cell lie at the base of
Fig. 32.
* Loeb, Pftuger's Archiv, Vol. 66, p. 439, 1897.
t Gotschlich, Pfiuger's Archiv, Vol. 56, p. 355, 1894.
148
DYNAMICS OF LIVING MATTER
«, « »i»i»i«i«i»i»i»i«i»m«
Fig. 33.
each cell of the tip of the stem (Fig. 32). If, however, the stem is put
into a horizontal position, these heavier particles will go to the peripheral
side of the cells on the lower half of the tip and to the central side of
the cells on the upper half of the tip (Fig. 33). This difference in the
position of these solid particles
may determine differences in the
reaction velocity of the chemical
processes in both groups of cells.
In the cells on the upper side
the heavier elements are in more
direct contact with the substances
diffusing into the cells from the
pith, while in the cells on the under side the reverse is true. These
assumptions are purely speculative, serving only as an illustration of
the statement that a change in the position of an organ might influence
the reaction velocity on the upper and lower sides of the organ differ-
ently. In consequence of such an influence, a curvature like that in
heliotropic reactions might be produced.
Czapek has found chemical differences between the tips of roots
which were put into a horizontal position and those left in their normal
vertical position. In the extreme tips of the positively geotropic roots
of Lupinus albus the amount of homogentisinic acid increased about
15 per cent in about half an hour when put into a horizontal position.
At the same time, a retardation in the blueing of tincture of guaiacum
was noticeable, which he considered the effect of the formation of an
antioxidase.* It is, however, questionable, whether these chemical
changes are responsible for the geotropic curvature. In order to prove
this it would be necessary to show a chemical difference in the lower
and upper sides of a root or stem which had been put or brought into
a horizontal condition. Czapek, however, states that he could not
find any difference between the upper and lower sides.
Animals also show geotropic phenomena.f Antennularia, a Hy-
droid, behaves toward gravitation like a geotropic plant, and it would
be possible to demonstrate the principle of geotropic curvatures in this
animal. When the stem of Antennularia antennina, which normally
grows vertically upward, is put into an oblique position in the aqua-
rium, the tip bends until it is again in a vertical position, and then con-
tinues to grow in this direction vertically upward. The roots are not
quite so straight as the main stem, and although thev have a tendency
* Czapek, Ber. der deutsch. bot. GeselL, Vol. 20, p. 464, 1902. He obtained similar
results in a case of light effects ; ibid., Vol. 21, p. 243, 1903.
f Loeb, Sitzungsber. der physik. med. Gesellsch., Wiirzburg, January, 1888; and
Pfliiger's Archiv, Vol. 49, p. 175, 1891.
TROPISMS AND RELATED PHENOMENA 149
to grow down vertically, the geotropic reaction is not so precise as in
the stem. The latter is negatively, the former, positively, geotropic.
In free-moving animals, geotropism is not so rare ; Cucumaria cucumisy
a Holothurian, possesses five rows of feet with which it can creep on ver-
tical surfaces. If the animal be put on a vertical glass plate, it will
creep vertically upward. When the plate is turned very slowly around
a horizontal axis, the animal remains quiet during the rotation, but as
soon as the plate is fixed, the Cucumaria again creeps vertically up-
ward. This occurs also in the dark room. We will call such animals
that are compelled to creep vertically upward, negatively geotropic.
Many marine animals and many insects show this reaction. If
free-swimming aquatic animals which show a tendency to gather at
the top or the bottom of a vessel are used for experimentation, the ex-
perimenter must be careful not to mistake the passive sinking or rising
of such forms for geotropic reaction. Ostwald has called attention
to the fact that with increasing temperature the internal friction of the
water diminishes rapidly, which necessitates that organisms which
float at the surface at a lower temperature must either sink down at a
higher temperature, or are unable to work upward, on account of the
diminished internal friction of the water. In addition, the resistance
due to the shape of the animal plays a role in these phenomena.*
The attempt which many animals make to keep the axes of their
eyes as nearly as possible in their normal position in space when the
body is put into an abnormal position, is a common reaction which
seems to be determined by gravitation. In Crustaceans the eyestalks
form a small angle with the horizontal plane when the animal is in its
normal position. When turned on one side, however, so that the right
side is directly downward, the eyes no longer keep their symmetrical
position in regard to the plane of symmetry of the animal, but the right
eye is raised, the left lowered.f It looks as if the eyes had a tendency
to keep their former normal position in space ; just as the root or stem
of a geotropic plant tries to keep its orientation toward the center of
the earth. This reaction of the eyes also exists in vertebrates, and
can be nicely demonstrated in fishes, lizards, birds, or rabbits. In
frogs the eyes do not show the so-called compensatory motions, but
the head as a whole tries to keep its normal orientation toward the
horizon, when the body of the animal is put into an abnormal posi-
tion. These reactions exist universally, but in such forms as possess a
powerful associative memory the reaction is liable to be interfered with.
* Wolfgang Ostwald, Zoologische Jahrlmcher, Vol. 18, p. 1, 1903.
t Clark, Jour, of Physiology, Vol. 19, p. 327, 1896. E. P. Lyon, Am. Jour. Physiology,
Vol. 3, p. 86, 1899.
150 DYNAMICS OF LIVING MATTER
Knight's experiment can be made in these forms. When they are
put on a rotating disk and turned in a horizontal plane, the eyes are
displaced during the rotation in the plane of the rotation, but in the
opposite direction.
In this case again a source of error has to be guarded against;
namefy, the influence of the retinal image. The tendency to keep the
eyes and the head in the normal position to the horizontal when the
body is turned, may be determined by the influence of the visual impres-
sions. The apparent motion of the objects on the retina when the
animal turns may cause a motion of the eye and head in the opposite
direction. This suspicion is the more justified as in some insects
these compensatory motions cease when the eyes are blackened.*
Lyon has, however, shown that in sharks and flounders these compen-
satory motions are not diminished when the optic nerves are cut.
In these forms at least we seem to deal with really geotropic reactions.
The next question must be, In which organs are these geotropic
reactions produced? The answer might be simple enough were this
field not in a hopeless state of confusion through the hypothesis con-
cerning the functions of the semicircular canals. Flourens had stated
that the sectioning of one of the semicircular canals causes the eyes and
head of the animal to move in the direction of the plane of the canal.
Goltz showed that destruction of the inner ear leads to disturbances
"of the maintenance of the equilibrium of the animal." This term,
"equilibrium," is not clear unless it be supplemented by the statement
"with reference to the horizon or to the center of the earth." Goltz
advanced the now famous hypothesis that semicircular canals are an
organ where the equilibrium of the head, and indirectly of the whole
animal, is regulated. If the head is bent, according to Goltz, the flow
of the lymph in the canals causes a stimulation of the nerve endings
in the ampullae of these canals, and this calls forth a reflex motion, by
which the head is put back into its normal position. Mach showed
that physical reasons prevented a flow of lymph such as Goltz's hypothe-
sis demanded; but that the pressure of the lymph against the nerve
endings in the ampullae, caused by changes in the position of the head,
might suffice to bring about the effects which Goltz's hypothesis de-
manded. He showed, moreover, that this hypothesis also demanded
that any stimulation of one of three ampullae only called forth a motion
of the eyes and head in the direction of the canal, and no other. While
this hypothesis at first met with general opposition, it was later accepted,
and it has, among others, received some support from my own
laboratory. Nevertheless, the hypothesis is wrong. Lyon has shown
* E. P. Lyon, loc. cit. Radl, Der Phototropismus der Thiere, Leipzig, 1903.
TROPISMS AND RELATED PHENOMENA 151
conclusively in my laboratory that the stimulation of the horizontal
canals in sharks and flounders calls forth motions of the eyes in the
plane of the canal, as the hypothesis demands, but that the two
other canals, or their ampullae, are either nonsensitive to stimula-
tion, or give no motion of the eyes or the head in the plane of the
stimulated canal. I will confess that I did not at first credit Lyon's
statements, but I have convinced myself that he is unquestionably
right. It seems that all the authors who had stated that stimulation
of one of the semicircular canals caused motions of the eyes or head
in the plane of the canal, based their statements only on the effects
of the stimulation of one of the three canals; namely, the horizontal.
The negative or questionable results they obtained in the case of the
two vertical canals they did not dare to accept in the face of the strik-
ingly clear results the horizontal canal yielded.* Suggestion does not
play a role in ordinary matters only, but occasionally also in science.
It is, however, possible that the compensatory motions and reactions
are after all produced in the inner ear, although the semicircular canals
have little or nothing to do with it. This follows from the fact that
when the auditory nerve in a shark is cut, all the compensatory motions
cease. f It may be that the otoliths in the inner ear are responsible for
this effect. Mach J was the first to point out this possibility, and De-
lage § made a number of experiments which seemed to speak in favor
of this view. The most striking experiment was made by Kreidl on
Palcemon. The otolith organs of this Crustacean are found in the
basal part of the small antennas. Palamon loses its otoliths during the
process of moulting, and after moulting it repairs the loss by putting
small granules of sand into the ear. Kreidl kept such Crustaceans in
vessels which were free from sand, but which contained instead very
finely powdered iron. After moulting the animals put this iron powder
into their ears. It was possible to test in such animals the otolith-
hypothesis of the geotropic reaction. The otolith rests on cells in which
the sense nerves end. They are therefore supposed to press upon the
nerve endings. When the animal is laid on one side, the otolith, instead
of pressing, will pull at the cell, and this causes a change in the nerve
endings which results in a righting motion (compensatory motion) of
the eyes, or, if possible, of the whole body. If this view were correct,
it should be expected that a magnet could produce effects similar to
* It is much easier to ascertain motions of the eyeball from right to left or vice versa
than up and down. This is due to the fact that we estimate the motion from the displace-
ment of the sclerotic. In the upward and downward motions, however, the sclerotic is, as
a rule, not visible.
f Loeb, P/Higer's Archiv, Vol. 49, p. 179, 1891 ; and Vol. 50, p. 66, 1891.
\ Mach, Grundlinien der Lehre von den Bewegungsempfindungen, Leipzig, 1875.
§ Delage, Archiv. de Zoologie experimental, Vol. 5, 1887.
152 DYNAMICS OF LIVING MATTER
gravitation, when the otoliths were of iron. If, e.g., the magnet were
approached from the right side of the animal, the iron otolith would be
pulled toward the right, and this should result in a reflex turning of the
animal upon its left side. Kreidl found indeed that this occurred.*
Kreidl's experiments were repeated and confirmed by Prentiss.
Delage, Kreidl, and Lyon all agree that the "maintenance of equi-
librium " or more correctly speaking the geotropic reactions of the
animal do not entirely disappear when the small antennae are cut off.
This proves that another organ contributes to these reactions, namely,
the eyes. Removal of the eyes and the antennas does away with the
compensatory motions.
While it is thus probable that the otoliths have something to do
with the reactions of the animal, it does not seem as if this were gen-
erally the case. The flounder possesses a single large otolith in each
ear, which can easily be extracted without injury to the ear. Lyon
found that if the otoliths were removed, the geotropic reactions and
"maintenance of equilibrium" were not disturbed.
This field requires further investigation, and I should not be sur-
prised if it were found that the really geotropic reactions of animals
were determined in certain cells of the inner ear, or in certain cells of
the brain, while otoliths may or may not act in an accessory way. It
would, however, be a mere anthropomorphism to assume otolith organs
inside the cells (as some botanists now begin to do for plants). Inside
of the cells of geotropically sensitive organs gravitation may probably
act through an influence upon the reaction velocity of certain chemical
processes, as set forth at the beginning of this chapter.
4. Chemotropism and Related Phenomena
Theoretically we may assume that if substances diffuse in air
or in water, the particles move in a straight line away from the center
of diffusion. If they strike an organism whose surface is affected
by the diffusing substances on one side only, the contractile proto-
plasm, or the muscles, turning the tip or the head or the whole organ-
ism toward that side, are thrown into a different state of contraction
from their antagonists. The consequence is a turning or bending
of the tip or the head until symmetrical points of the chemically sen-
sitive surface of the body are struck by the lines of diffusion (or the
diffusing particles) at the same angle. As soon as this occurs the con-
tractile elements on both sides of the organ, or organism, are in an equal
* Kreidl, Sitzungsber. der Wiener Akademie der Wissensck., Vol. 102, Abth. 3, p. 149,
1893.
TROPISMS AND RELATED PHENOMENA 153
state of contraction, and the animal will bend or move in the direction
of the lines of diffusion. There is practically, however, this difficulty;
namely, that the lines of diffusion are generally disturbed by currents
due to changes and variations in temperature, and instead of the straight
lines of force we have in this case often irregular and changing ones.
This makes it a priori hopeless to expect that in the case of chemo-
tropism the organisms move in as straight a line as in that of heliotro-
pism, geotropism, and certain cases of galvanotropism. In the majority
of cases we are also dealing with a response to sudden changes in the
nature and concentration of the substances contained in the medium.
Engelmann was probably the first to call attention to this type of
phenomena. He found that certain bacteria and Infusorians gather
around a source of oxygen.* In this case it was evidently a response
to changes in the concentration of the oxygen, the organisms coming
to rest where the tension of oxygen was a relative maximum. Pfeffer
first compared these phenomena with those of other tropisms in his
classical paper "Oriented Locomotor Motions produced by Chemical
Stimuli." f He showed that the zoospermia? of ferns, mosses, and other
plants move toward points from which certain substances diffuse into
the water in which these organisms are. Pfeffer found that such effects
are produced upon spermatozoa of ferns by malic acid and its salts,
and upon those of mosses by cane-sugar solutions. The biological
importance of this observation lies in the fact that malic acid is com-
paratively common in plants, and the presence of this acid in the arche-
gonia of the ferns possibly contributes toward bringing the sperm to
the egg. From the normal archegonium no mafic acid diffuses, but
those ready to be impregnated let part of their contents diffuse. The
appearance of Pfeffer's paper aroused in many the hope that it might
be shown that the animal egg, too, attracted the spermatozoa in some
such chemotropic or chemotactic way; but all the experiments thus
far made in this direction by J. Dewitz, Buller, and others — I have
made quite a few experiments myself on this subject — have without
exception shown that such is not the case in the eggs thus far tried.
There does not seem to exist an attraction of the spermatozoa on the
part of the egg, but the meeting of spermatozoa and the egg is left to
chance, except that automatic tropismlike mechanisms exist, whereby
the ripe males gather near the ripe females and the sperm is shed in the
neighborhood of the egg. Pfeffer's method consisted in introducing
a solution of the chemical substance to be tested, e.g. malic acid, into
* Engelmann, Pfliigers Arckiv, Vol. 25, p. 2S5, 1SS1: Vol. 26. p. 537, 1SS1 ; and
Vol. 29, p. 387, 1882.
t Pfeffer, Unters. aits dem bot. Institut in Tubingen, Vol. I, p. 363, 1SS1— 18S5.
154 DYNAMICS OF LIVING MATTER
a capillary tube which was sealed at one end, and then putting the tube
with the open end into the water which contained the spermatozoa.
"When the liquid in the tube contains only o.oi per cent malic acid,
the spermatozoa (of ferns) very soon move toward the opening of the
capillary tube. At the same time many spermatozoa move into the
capillary tube and within from five to ten minutes many hundreds of
spermatozoa may accumulate in the tube. The malic acid acts as
well in the form of a free acid as in the form of salts, and that it is a
specific stimulant may be seen from the fact that in the same time prob-
ably not a single spermatozoon enters a capillary tube containing pure
water or a solution of other substances." Massart and Bordet used
this method of Pfeffer's on leucocytes.* It had been known for a long
time that in inflamed tissues the number of leucocytes increases, and
it was generally admitted that at least part of the supernumerous leu-
cocytes migrate there from the capillaries. In order to answer the
question as to what causes this migration, Massart and Bordet put
capillary tubes containing cultures of bacteria, especially staphylo-
coccus pyog. aureus into the abdominal cavity of the frog. After twenty-
four hours the authors found leucocytes in large numbers in the tube.
If a sterile culture medium was introduced, no leucocytes migrated into
it. This seems to indicate that substances produced by the bacteria
determine the direction in which the leucocytes move.
To give a more distinct picture of these phenomena I may mention
a few of the observations made by Garrey f on this subject. A small
square trough contained the organisms — in this case Chilomonas, an
Infusorian. At one side a small capillary tube was inserted, into which
the solution of the substance was put whose efficiency was to be tested.
At the beginning of the experiment the organisms were equally distrib-
uted all over the square space. When very dilute HC1 was put into
the capillary tube, a clear circular area entirely free of organisms was
soon formed around the opening of the tube. The organisms recede
from the HC1, diffusing into the trough, and thus indicate very nicely
the rapidity and extent of diffusion. This clear area increases until
the HC1 has diffused to the end of the square space, when the organ-
isms are again distributed equally. In this case we are probably not
dealing with a real tropism, but with a reaction to sudden changes
in the intensity of the stimulus. When the organisms go from neutral
water to sufficiently acidulated water, they are repelled. According
to Jennings, they swim first backward and then toward one side, a
* Massart and Bordet, Soc. Roy. des Sciences med. et nat. de Bruxelles, 3 Fevr., 1890.
Reviewed Physiol. Centralblatt, Vol. 4, p. 332, 1891.
t Garrey, Am. lour. Physiology, Vol. 3, p. 291, 1900.
TROPISMS AND RELATED PHENOMENA 155
reaction which is quite common among Infusorians, and to which
Jennings has given a special name, motor reflex or motor reaction.*
Garrey found that the phenomenon described above can be produced
by many inorganic acids, provided their concentration is n or
above. Alkalis bring about the same effect at a somewhat higher
concentration; namely, n. Salt solutions require a still higher
concentration, e.g. NaCl, and LiCl require a minimum concentration
of about — , and KC1 about — . MgCL, CaCL, SrCL, and Bad, acted
at a lower concentration ; namely, to . ZnSCX, ZnCL, CuSO.,
100 200 4 4
Til/ 77t
and AgNCX were effective in a concentration of ■ to .
•* 1000 2000
The immense biological role of these reactions is known to every one
who has worked with insects. The finding of food, the depositing of
eggs, and the meeting of the two sexes for the process of pairing are
determined to a large extent by diffusing substances. I may relate
the following observation f which certainly has been made often enough
before. A female butterfly was put into a small, closed wooden box
which was suspended from the middle of the ceiling of a room whose
windows were open. At first no other butterfly of the species to which
the female belonged was visible, but during the next half hour three
male butterflies of the same kind approached the house, stopped at the
window, then flew into the room, and settled on the wooden box through
the openings of which they tried to enter. This effect could have been
produced only by an emanation from the female butterfly. As an
example of how emanations direct the motions of females that are ready
to deposit their eggs, the fact may be cited that certain volatile sub-
stances emanating from meat "attract" the female fly. If fat and
meat of the same animal are put side by side on the window sill, the
female fly will light on the meat, where she deposits her egg, but not
on the fat. This tropismlike reaction guarantees the perpetuation
of the race, inasmuch as the larvae feed and develop on meat, but not
on fat.
5. Stereotropism (Thigmotropism)
Certain animals are compelled to put their bodies as much as pos-
sible into contact with solid bodies, while other organisms show the
* Jennings, Am. Jour. Physiology, Vol. 2, p. 374, 1899 ; and numerous subsequent papers
by the same author.
t Loeb, Animal Heliotropism and its Identity with the Heliotropism of Plants, Wiirz-
burg, 1889.
i56
DYNAMICS OF LIVING MATTER
reverse behavior. The former organisms I designated as positively,
the latter as negatively, stereotropic.
The first discovery in this direction was made by J. Dewitz,* who
found that the spermatozoa of the cockroach (Periplaneta orientalis)
are "attracted by surfaces." "If small pieces of glass or some other
object are placed between a slide and a cover- glass so that there is a
space between cover glass and slide, and if this space be filled with a
NaCl solution containing the spermatozoa, the latter gather only at
the cover glass and the slide. In the rest of the liquid no spermatozoa
are found. If a glass bead be put into such a liquid containing sper-
matozoa, the latter in no case leave the surface of the bead, although
they are constantly in motion." Dewitz recognized that this reaction
was of the greatest importance for the entrance of the spermatozoa
into the egg of the cockroach. This egg possesses a micropyle, and
only here can the spermatozoa enter the egg. When the egg is laid it
passes the duct of the seminal receptacle, where the female carries the
sperm it receives in the act of pairing. The egg then comes in contact
with the sperm, some of which is possibly pressed out of the receptacle
reflexly by the passing of the egg. When once on the surface of the
egg, the spermatozoa can no more leave it, but must move on its sur-
face incessantly. In this way one spermatozoon finally reaches the
micropyle and gets into the egg. The impregnation of the egg is there-
fore in this case a function of the stereotropism of the spermatozoa.
Although stereo-
tropism is no real
tropism, inasmuch as
in this case lines of
force do not exist, there
exist stereotropic curva-
tures. When the stems
of Tubularia are fixed
in an aquarium in such
a way that the polyp
touches the wall of the
aquarium (Fig. 34),
the polyp begins to
bend away from the
wall until at right
angles with it, and then continues to grow in this direction. The
stolon, however, sticks to the glass wall, possibly by the secretion of
a sticky substance.
* J. Dewitz, Pfliiger's Archiv, Vol. 37, p. 219, 1885; and Vol. 38, p. 358, 1886.
Fig. 34.
TROPISMS AND RELATED PHENOMENA 157
It had been known that a number of animals hide in crevices.
This phenomenon was generally ascribed to a supposed timidity or
photophobia of these animals, which were believed in this way to pro-
tect themselves from their enemies. I showed that in this case the ani-
mals are forced to bring their bodies as much as possible in contact
with solid bodies. Amphipyra is an outspokenly positively heliotropic
butterfly which has a tendency to creep into crevices. If a number
of these animals are kept in a box and a plate of glass is put on the
bottom of the box so that it rests upon pieces of glass just high enough
to allow the Amphipyra to creep under the glass plate, all of the butter-
flies will be found after a time collected under the plate. This happens
as well when they are in the dark as when the plate of glass is exposed
to full sunlight. As long as they cannot creep into crevices they run
around restlessly, while they become quiet as soon as their bodies come
in contact on all sides with other solid bodies.
The crevices thus act like a trap where such animals are gradually
caught until metabolic changes (need of food) again make them rest-
less, and compel them to move about.*
A similar form of irritability exists in ants. When sexually mature
ants are kept in boxes containing pieces of folded paper or cloth, all of
these animals will be found after some time in the folds, even if the
box is absolutely dark. This form of reaction leads to the foundation
of a nest, inasmuch as the female, after pairing, creeps into a crevice,
where it lays its eggs.
This form of irritability is also found in worms. If, e.g., earth-
worms are kept in a glass vessel with a horizontal bottom and vertical
walls, they collect and crawl in the angle between the vertical and
horizontal side. Experiments which S. S. Maxwell made on Nereis,
a marine Annelid, show how great the force is which keeps such animals
in contact with solid bodies. These animals burrow in the sand. If
they are kept in a porcelain dish, into which a number of glass tubes
have been put which are just large enough to allow a Nereis to enter,
it will be found that in about twenty-four hours each tube will contain
a Nereis. The animals cannot even be induced to leave the tube if
the latter is exposed to direct sunlight, which kills them, although by
crawling out they might save their lives. f There are other forms
which avoid contact with solid bodies as persistently as the animals
thus far mentioned seek it. This form of irritability, negative
stereotropism, is found in many swimming forms, e.g. the nauplii of
Balanus.
* Loeb, Der Heliotropismus der Thiere. 1889.
t S. S. Maxwell, Pfluger's Archiv, Vol. 67, 1897.
158 DYNAMICS OF LIVING MATTER
Positive stereotropism is apparently that form of irritability which
next to chemotropism is most instrumental in bringing about the union
of the two sexes. The holding of the female by the male during copu-
lation is evidently in many forms purely a form of stereotropism. In
frogs such contact irritability develops during the spawning season,
on the ventral side of the chest. At that time the contact of the ventral
side of the chest with any solid body causes a reflex closing of the arms
of the male frog around the solid body. The embrace becomes lasting,
however, only in case the embraced object is a female frog. In this
case, obviously, other stimuli contribute toward making the embrace last-
ing. What the nature of, these stimuli is, is not yet known.* Holmes
has called attention to the fact that the embrace of the female Gammarus
by the male is a similar case of stereotropism.f These reactions can
even be demonstrated in the decapitated frog.
6. Concluding Remarks concerning Tropismlike Reactions
It is obvious that the tropisms furnish the understanding for many
purposeful instinctive reactions, and that what is generally called an
instinct is often nothing more than a compulsory turning and moving of
an organism in a given direction. I have carried out such an analysis
of animal instincts in another book, and therefore do not wish to enter
upon this subject here. I believe, indeed, that the tropisms and trop-
ismlike reactions will one day form the main contents of a scientific
psychology of lower forms. The tropisms, however, and tropismlike
compulsory reactions also play a role in the mutual arrangements of
organs and tissues. The first case of this kind mentioned was the
observation that the tigerlike coloration of the yolk sac of the Fundulus
embryo is due to a creeping of the chromatophores upon the blood
vessels. At first the chromatophores and blood vessels are formed with-
out any definite relation to each other, but by and by every chromato-
phore creeps on the capillary, enveloping it completely .$ I am not able
to state whether this is a case of chemotropism caused by the oxygen in
the capillary tubes, or a case of stereotropism. Driesch § suggested
later that the migration of the mesenchyme cells to those spaces in the
gastrula of the sea urchin where the skeleton is to be formed, might
be due to a tropism. Herbst || has pointed out the possibility of a wide
application of the tropisms in ontogenetic processes.
* Goltz, Beitr'dge zur Lehre von den Nervencentren des Frosches, Berlin, 1869.
t S. J. Holmes, Biological Bulletin, Vol. 5, p. 288, 1903.
% Loeb, Pfliiger's Archiv, Vol. 54, p. 525, 1893; and Jour, of Morphology, Vol. 8, p. 161,
1893. § Driesch, Archiv fur Entivickelungsmechanik, Vol. 3, 1896.
|| Herbst, Ueber die Bedeutung der Reizphvsiologie filr die causale Auffassung der
Ontogenese, Biologisches Centralblatt, Bd. 14 and Bd. 15, 1894 and 1 895.
TROPISMS AND RELATED PHENOMENA 159
The more fertile a principle is, the more we can afford to be conserva-
tive in applying it. It is obvious that certain reactions have been called
tropisms which have nothing to do with them; possibly Roux's cyto-
tropism belongs to this group. Roux has observed motion of the cleav-
age cells of the germ of the frog's egg to and from each other; he has
called these cases cytotropism. Driesch has pointed out that these are
phenomena which are caused purely by capillary forces between the eggs.
If this be correct, as it seems to be, and if we are not dealing in this case
with a reaction of living matter to an outside stimulus, we are not deal-
ing with a tropism ; for by the latter we mean distinctly a class of com-
pulsory reactions of the organism to outside stimuli ; but not the passive
motions of bodies caused by capillary forces. That these bodies consist
of living protoplasm does not influence this discrimination.
Another warning to be careful in applying this principle was shown
by recent investigations of E. P. Lyon.* It is a well-known fact that
many fishes put their bodies into the direction of a current of water, and
try to swim against the current. It was commonly supposed that this
orientation was caused by the streaming of the water, possibly its fric-
tion against the sides of the body. Lyon has shown that this behavior
is an optical reflex caused by the apparent motion of the object while
the animal is moved passively by the stream. When he inclosed the
fish in glass jars and dragged these jars through the water, the fish inside
the jars oriented themselves in the direction opposite to that in which
the jar was moved. There is no objection to calling this a tropic re-
action, but it is certain that it should no longer be called rheotropism.
Attention should also be called to the fact that while the tropisms
form in many cases the mechanism by which the preservation of the
individual and the species is brought about, there are many cases of
tropism which are of no use to the species; the whole field of galvano-
tropism is an example of this. Galvanotropism is purely a laboratory
phenomenon; outside of the laboratory no animal ever comes into a
situation which might call forth a galvanotropic reaction; yet galvano-
tropism is not uncommon among animals. Among the positively helio-
tropic animals, we find forms which are never exposed to the light, e.g.
the caterpillar of the willowborer, or Cuma Rathkii, a Crustacean which
lives in the mud at Kiel. I pointed out sixteen years ago that these
cases speak against the assumption that the tropisms could have been
acquired by the way of natural selection,! and Morgan has recently
taken the same ground ; J but I do not wish to enter upon a criticism of
* E. P. Lyon, Am. /our. Physiology; Vol. 12, 149, 1904.
f Loeb, Der Heliotropismus der Thiere, 1889.
% T. H. Morgan, Adaptation and Evolution, New York, 1904.
160 DYNAMICS OF LIVING MATTER
the principle of natural selection, which has certainly been a factor in
the elimination of forms, although it played no role in producing any
qualities or irritabilities. The fact that cases of tropism occur even
where they are of no use, shows how the play of the blind forces of na-
ture can result in purposeful mechanisms. There is only one way
by which such purposeful mechanisms can originate in nature;
namely, by the existence in excess of the elements that must meet
in order to bring them about. In green plants and in some animals
the positive heliotropism is useful; yet there exists probably an endless
number of heliotropic animals for which their heliotropism is about as
useless as is galvanotropism. The prerequisites for heliotropism are a
symmetrical body form, which seems to be present in almost all organ-
isms— although some asymmetries exist — and the presence of photo-
sensitive substances, which is not quite so common, but certainly not
infrequent. Some of the regular substances found in protoplasm seem
to turn readily into a photosensitive form. As the two conditions men-
tioned above are quite common, the laws of probability make it neces-
sary that in a certain number of cases both conditions will be fulfilled,
and then we may expect heliotropic actions. If it now occurs that in
an organism the turning to the light helps it to find its food, as is the
case with certain caterpillars, e.g. Porthesia chrysorrhcea, or the stems of
green plants whose starch is manufactured by light, we have a "purpose-
ful mechanism." Again, according to the laws of probability, the number
of animals in which the three groups of conditions meet is much smaller
than where only two meet. The tropisms thus furnish an insight into
the origin of purposeful reactions by the blind forces of nature.
LECTURE IX
FERTILIZATION
i. The Specific Character of the Fertilizing Power of the
Spermatozoon
It is comparatively easy for the physicist to give to his data the form
of a mathematical law, inasmuch as the independent variables are
mostly in evidence, and all that remains to be done is to find the formula
which expresses the relation between the variable and the function. In
biology the independent variable is generally unknown, and the main
energy of the investigator must be devoted to discovering this variable.
The history of the problem of fertilization is extremely instructive in
this regard. Although the fact that many animals, e.g. fishes, birds,
etc., develop from an egg has been known as long as man has observed,
it was not until 1827 that von Baer discovered the mammalian egg;
and although Leuwenhoek, or a pupil of his, discovered the existence
of spermatozoa in the sperm as early as 1677, it was not until 1843 that
the fact was really established that generally the development of the egg
is caused by the entrance of a spermatozoon.
As far as we know at present the entrance of a spermatozoon
into the egg has two kinds of effects which must be kept apart : the first,
namely, the starting of the process of development, the developmental
effect; the second, the transmission of the paternal qualities to the
new organism, the hereditary effect. We shall first discuss the develop-
mental effects of the spermatozoon upon the egg, raising the question
whether this effect of the spermatozoon is specific or general ; that is to
say, whether a spermatozoon can cause only the development of an egg
of the same species or of any egg. It is well known that animals belong-
ing to the same family, e.g. various kinds of dogs, the horse and the
donkey, can be successfully crossed. In fishes, also, it has long been
known that various types of hybrids can be easily obtained. Spallan-
zani and other observers were never able to obtain hybrid larvas among
the Batrachians. Pfliiger, however, found that the first segmentations
can be produced in the eggs of Rana jusca by the sperm of a salamander
m 161
1 62 DYNAMICS OF LIVING MATTER
{Triton alpestris). When the eggs of the toad (Bujo vulgaris) are fer-
tilized with the sperm of Rana fusca, they develop beyond the morula
stage.* Born hybridized various kinds of toads. f
It is rather remarkable that all these experiments seemed to indicate
that the fertilizing power of a spermatozoon is quite specific, and that
it does not go beyond the closely related forms. It was of considerable
interest to find out whether the stimulating power of a spermatozoon
might not be extended to more distant species. Nobody had succeeded
in fertilizing the eggs of the sea urchin with the sperm of the starfish,
and I had myself vainly tried to accomplish this result until it occurred
to me that by altering the constitution of the sea water this result might
be accomplished. The sea water has normally a practically neutral
reaction. If, however, just enough NaHO or Na2C03 is added to
make its reaction faintly alkaline, the eggs of the sea urchin, Strongylo-
centrotus purpuratus, can be fertilized by the sperm of every starfish
which has thus far been tried, and by that of Ophiurians.% It suffices
for this purpose to add i to 2 c.c. — NaHO to 100 c.c. of sea water.
10
The relative number of sea-urchin eggs that can be fertilized in this way
by the sperm of starfish or brittle star varies for various forms. With
the sperm of Asterias ochracea, Asterias capitata, and an Ophiurian, as
many as 50 per cent of the eggs could be fertilized, while with the sperm
of the twenty ray starfish (Pycnopodia spuria) only 5 per cent, and with
the sperm of Asterina only 1 per cent. In normal sea water only ex-
ceptionally an egg of Strongylocentrotus is fertilized by the sperm of
Asterias; and in this case the- fertilization occurs very late," — from
twelve to thirty-six hours after the sperm has been added. The sperm
of Pycnopodia and Asterina was never able to cause a fertilization of
the sea urchin's egg in normal sea water.
It seems that the increase in the alkalinity of the sea water increases
only the fertilizing power of the spermatozoon, and not that of the egg.
When the sperm of starfish is introduced into alkaline sea water in which
there are eggs of Strongylocentrotus, it takes from five to eight minutes
before the fertilization membrane — which indicates the entrance of a
spermatozoon into the egg — is formed. After a short time, which
varies with the concentration of the HO-ions in the sea water, the sperm
loses its fertilizing power, and the spermatozoa agglutinate with each
other. The eggs, however, do not lose their power of being fertilized
by remaining in this abnormal solution. If the spermatozoa of the star-
* Pfluger's Archiv, Vol. 29, p. 48, 1882.
t Born, ibid., Vol. 32, p. 453, 1883.
\ Loeb, University of California Publications, Vol. I, pp. I, 39, 85. Pfluger's Archiv,
Vol. 99, pp. 323, 637; Vol. 104, p. 325, 1904.
FERTILIZATION 1 63
fish are brought from the alkaline sea water into normal sea water
which contains the eggs of the sea urchin, none or only a few eggs are
fertilized, showing that only in the alkaline sea water does the sperm
of the starfish possess the qualities necessary for the fertilisation of
the egg of the sea urchin.
It is not so easy to decide which change must occur in the sperm of
the starfish in order to enable it to fertilize the egg of the sea urchin.
It is certain that the addition of alkali increases the energy of the mo-
tions of the spermatozoa of the starfish, but it is also certain that the
addition of bicarbonate to sea water brings about an equal or a still
more powerful increase in the energy of the motions of the spermatozoa
of the starfish without increasing their power of fertilizing the eggs of
the sea urchin. At present it is generally assumed that all that is neces-
sary for the entrance of the spermatozoon into the egg is the ciliary
motion of the spermatozoon which brings it in contact with the egg,
and that the entrance of the spermatozoon into the protoplasm of the
egg is due to the energy of its ciliary motion. I consider it possible on
the basis of these observations that the ciliary motion of the spermato-
zoon is required only to bring spermatozoon and egg protoplasm into
close contact, and that the entrance of the spermatozoon into the inte-
rior of the egg protoplasm is due to surface tension forces. It is
not impossible that the conditions for this process depend upon the sur-
face tension between spermatozoon and sea water becoming greater
than the sum of surface tensions between sea water and egg, and sper-
matozoon and egg. In this case the egg protoplasm must spread at
the limit between spermatozoon and sea water. The spermatozoon is
thus introduced into the interior of the egg. These ideas are supported
by the fact that the spermatozoon of the starfish fertilizes the eggs of
its own species in normal sea water, and that the process is not aided
by making the sea water alkaline.
It is also hardly necessary to mention the fact that the eggs of Strongy-
locentrotus purpuratus can be best fertilized in neutral sea water, not in
alkaline sea water. It is a surprising fact that in the alkaline sea water
in which the fertilization of the sea urchin's egg by starfish sperm succeeds
best, the fertilization of the same egg by sperm of their own species is
rendered difficult or impossible. This may be due to the fact that the
motility of the spermatozoa of the sea urchin is diminished by the alka-
line sea water.
I have tried to fertilize the eggs of the sea urchin with the sperm of
Annelids and Mollusks, but thus far without success. It therefore looks
as if the fertilizing power of a spermatozoon were to some extent at
least specific. It is also possible, however, that if our idea concerning
164 DYNAMICS OF LIVING MATTER
the role of surface tension for the entrance of the spermatozoon is cor-
rect, these restrictions to the fertilizing power of the spermatozoon are
only apparent, and that we have only to find modifications of the natu-
ral media, which allow the spermatozoon to enter the eggs of foreign
species.
As a rule only one spermatozoon enters an egg : as soon as this has
entered no further spermatozoon can enter. This is also true for frag-
ments of an egg. First, O. and R. Hertwig and later Boveri, Delage,
and many other authors showed that a piece of an unfertilized egg can
be fertilized by a spermatozoon. Janssens has recently observed that if
a piece of protoplasm be cut off from a fertilized egg, this can no longer
be fertilized. It is not impossible that the entrance of a spermatozoon
alters the surface tension of the protoplasm of the egg, making it thus
impossible for another spermatozoon to enter.
The egg of a starfish is, as a rule, not yet ripe, i.e. capable of being
entered by a spermatozoon immediately after it is taken from the ovary.
It has to lie for about two hours in sea water before it is ready for fertili-
zation. During this time the polar bodies are thrown out. Delage has
shown that if a piece of protoplasm be cut off from an egg of a starfish
(Asterias glacialis) before it is ripe, it cannot be fertilized by a sperma-
tozoon, but that this can be done when the piece of protoplasm is cut off
from the egg after the egg has gone through the process of maturation.*
It is generally stated that the pollen of a hermaphroditic plant can-
not fertilize the egg cells of the same individual. Castle found that
similar though less pronounced conditions exist in a' hermaphroditic
Ascidian ; namely, Ciona intestinalis. The eggs of a Ciona can, as a rule,
not be fertilized with the sperm of the same individual, while they can
be fertilized with the sperm of another individual. This immunity of
the eggs against sperm of the same individual is not without exception.
In some cases Castle found that 5, 10, or even 50 per cent of the eggs
of an individual could be fertilized with sperm of the same individual.
Morgan confirmed Castle's observations, and found that if the eggs are
put for about ten minutes in a 2 per cent ether solution in sea water, in
a number of (but not in all) cases the number of fertilized eggs shows a
slight increase, f
2. Artificial Parthenogenesis and the Theory of Fertilization
It is hardly necessary to state that at all times authors have been
ready to explain the fertilizing or developmental action of the sper-
* Delage, Archiv. de Zool. experimentale, Vol. 7, pp. 383, 5 1 1.
t Morgan, Jour, of Exper. Zool., Vol. I, p. 135, 1904.
FERTILIZATION- 165
matozoon. One such explanation states that the spermatozoon im-
parts a peculiar mode of motion to the egg, leaving it to science to find
out what this mysterious motion is. Other authors say that the egg is
comparable to a watch which cannot go unless a spermatozoon enters,
leaving it to science to find out the wheels and the spring in the egg, and
the relation of the spermatozoon to this mechanism. Others again say
that the spermatozoon exercises a stimulus, forgetting, however, to
tell us what is the nature of the stimulus. The list of such expla-
nations might be continued, but they all show the same characteristic;
namely, that an explanation by phrases or words is offered where
an explanation by facts is wanted. Instead of devoting any time to
this kind of metaphysics, we shall consider some of the facts of par-
thenogenesis.
The oldest and best-known case of parthenogenesis is that of
plant lice {Aphides). When the temperature and moisture are suffi-
ciently high, the Aphides reproduce themselves parthenogenetically.
Males do not exist under such circumstances. This condition can be
maintained for years, possibly indefinitely. Similar cases of partheno-
genesis seem to occur in Daphnia. A remarkable case of parthenoge-
netic development occurs among bees (and possibly among social wasps),
where, according to Dzierzon, the male bees originate from unfertilized
eggs, while the female (queens and workers) originate from fertilized
eggs. The queen pairs only once and the sperm is carried in a recep-
tacle. When an egg passes the duct without any sperm coming from
the duct, it remains unfertilized. Dzierzon found that old queens lay
only eggs from which male bees develop, and the examination of the
receptacle showed that in such cases the receptacle was free from sperm.
It was, moreover, observed that the workers, whose rudimentary sexual
organs exclude copulation, occasionally lay eggs from which, however,
only male bees originate. The observations of Dzierzon were confirmed
and enlarged upon by Siebold, Leuckart and very recently by Petrun-
kewitsch.
In such cases of parthenogenesis the development of the egg is not
called forth by a spermatozoon, but by another, at present, unknown
condition. More recently the fact has been established that eggs, which
naturally develop only when a spermatozoon enters, can be caused to
develop artificially by certain physical and chemical means. In 1886
Tichomiroff published the fact that the unfertilized eggs of silkworm,
Bonibyx mori, can be caused to develop by rubbing them gently with a
brush, or by putting them for a short time into concentrated sulphuric
acid. Siebold had already mentioned, and Nussbaum confirmed his
observation, that a small number of such eggs develop without these
1 66 DYNAMICS OF LIVING MATTER
means.* The publication of Tichomiroff caused Dewitz to make simi-
lar experiments on the eggs of frogs, and he believed that he found that
treatment of these eggs with corrosive sublimate caused them to seg-
ment! Roux, however, showed that Dewitz's conclusion was based
upon an error, inasmuch as the eggs did not segment, but underwent
coagulation, which gave the surface of the egg occasionally the appear-
ance of having segmented.
A Russian author, Kulagin, made the statement that he put fish eggs
into diphtheria antitoxine and saw a segmentation ; but inasmuch as he
published but this one statement on the subject, it is hard to tell whether
or not sources of error were sufficiently avoided.
In 1887, O. and R. Hertwig published their well-known experiments
on the effects of various poisons on the segmentation of the eggs of Echino-
derms. During these experiments, R. Hertwig made the observation
that if eggs are transitorily treated with a 0.1 per cent solution of sul-
phate of strychnia, and are then put back into sea water, these eggs
show karyokinetic figures, and occasionally segment. This observa-
tion was repeatedly discussed by him in subsequent papers.^ Hertwig
raised the question whether other media might not have similar effects.
Mead§ found in Woods Hole, that if a little KC1 is added to sea water,
the eggs of Chcetoptorus, a marine Annelid, throw out their polar bodies,
a process which in this form is normally only produced by the entrance
of a spermatozoon into the egg. NaCl has no such effect. Morgan
tried the effect of the addition of NaCl and other salts to sea water on
unfertilized eggs of sea urchins, in order to test some statements made
by myself and Norman concerning the effects of these salts on fertilized
eggs. He found that unfertilized eggs form artificial astrospheres in such
solutions, || and afterward!! made the important observation that if these
eggs are put back into normal sea water, they may begin to segment.
He states, however, that "the result is a mass of extremely minute
granules or pieces. These pieces never acquire cilia and do not produce
any form that resembles any stage of the normal embryo. Later the
masses disintegrate " (p. 454). The pathological cases of tumors,
or galls show also that cell division and growth may be produced
which do not lead to the formation of an embryo.
I was led to try experiments on artificial parthenogenesis in order
* M. Nussbaum, Archiv fur mikrosk. Anat., Vol. 53, p. 444, 1899.
t J. Dewitz, Biol. Centralblatt, Vol. 7, p. 93, 1887.
X R. Hertwig, Ueber Befruchtung und Conjugation, Verhandl. der deutsch. zoolog.
Gesellsch., 1892; and Sitzungsber. der Gesellsch. filr JMorphologie und Physiologie, in
Munchen, 1895 ; and Festschrift fur Gegenbauer, Vol. 2, p. 23, 1896.
§ A. D. Mead, Lectures Delivered at Woods Hole, Boston, 1898.
|| T. H. Morgan, Archiv filr Entwickelungsm echanik, Vol. 3, p. 339, 1896.
If T. H. Morgan, Archiv fur Entzvickelungsmechanik, Vol. 8, p. 448, 1899.
FERTILIZATION 1 67
to test the idea of the role of ion-proteids in the mechanism of living
matter. If it were true that the salts played the role which I was in-
clined to ascribe to them, it might also be possible to cause with their aid
the normal development of eggs. The experiments did not sustain this
idea as I had expected, but I succeeded in producing plutei from the
unfertilized egg of the sea urchin by exposing the eggs for about two
hours to sea water whose concentration had been raised by about 40
per cent to 50 per cent. It was immaterial which substance was used
to raise the concentration of the sea water, except for the fact that no
substances could be used which injured the eggs too much. The best
effects can be produced by raising the concentration of the sea water
through the addition of NaCl.*
When unfertilized eggs are put into hypertonic sea water, they lose
water and shrink. When put back into normal sea water, they absorb
water again. We must therefore raise the question as to which of these
two conditions causes the egg to develop, the loss of water when the egg
is put into the concentrated sea water, or the taking up of water when
it is put back into normal sea water. It can be shown that the former
is the cause. If we increase the concentration of the sea water less
than 40 per cent, if e.g. we add 7 c.c. of a 2\ m solution of NaCl to 93 c.c.
of sea water, some of the unfertilized eggs of Arbacia will develop into
swimming blastulae, even if left permanently in the hypertonic sea water.
I have recently repeated this experiment with the eggs of Strongylocen-
trotus. If the eggs of this sea urchin were left in a mixture of 100 c.c.
sea water + 5 c.c. 2J « NaCl solution, after about six hours segmenta-
tion began, and after one or two days swimming larvae began to appear.
These larvae, however, did not develop into gastrulae or plutei, probably
on account of the abnormal condition of the sea water. In this case
only a loss, but no taking up, of water occurred. When the unfertilized
eggs of the sea urchin are put permanently or transitorily into sea water
which is diluted with distilled water, no development is produced.
But although the osmotic method led to the development of larvae
from the egg, it differed in a number of points in its effects from the pro-
cess of fertilization by spermatozoa. In the first place, the eggs fertilized
with sperm form a characteristic membrane as soon as the spermatozoon
has entered, while the unfertilized eggs treated with hypertonic sea water
develop without the formation of a membrane. Second, the rate of
development is considerably faster in the fertilized egg than in the egg
caused to develop parthenogenetically. Third, the larvae originating
from fertilized eggs rise to the surface of the water as soon as they begin
* Loeb, Am. Jour. Physiology, Vol. 3, p. 135, 1899; Vol. 3, p. 434, 1900; Vol. 4,
p. 178, 1900; and Science, Vol. 2, p. 612, April, 1900.
1 68 DYNAMICS OF LIVING MATTER
to swim, while those originating by the above-mentioned osmotic pro-
cess swim at the bottom of the dish. Fourth, the number of larvae
developing from fertilized eggs is, as a rule, practically ioo per cent,
while in the case of artificial parthenogenesis a much smaller percentage
of the eggs develop into swimming larvae. In the case of Arbacia, I
often succeeded in causing more than 20 per cent of the unfertilized
eggs to develop, but in the case of Strongylocentrotus — the form of the
sea urchin common at Pacific Grove — I was rarely able to obtain even
as high a percentage of developing eggs. Often enough only a fraction
of 1 per cent of the eggs yielded swimming larvae by the osmotic
method of artificial parthenogenesis.
In thinking over the possible cause of this difference between the
development of the egg fertilized by sperm and of the egg caused to
develop by osmotic influences, it occurred to me that the spermatozoon
might carry into the egg not one, but several, substances or conditions,
each of which was responsible for only a part of the specific features of
sexual fertilization; and that in order to completely imitate the action
of the spermatozoon it might be necessary to combine two methods of
artificial parthenogenesis, each of which alone imitated the process of
sexual fertilization only partially. This latter idea proved correct far
beyond my expectations.*
I found that if the eggs of Strongylocentrotus purpuratus are put into
ft
50 c.c. sea water to which 3 c.c. — of a fatty acid, e.g. formic, acetic,
propionic, butyric or valerianic acid, are added, and are left in this
water for from one half to one and one half minutes, they form a mem-
brane when put back into normal sea water. The eggs go through the
internal changes characteristic of nuclear division, but they rarely seg-
ment. In about six hours they begin to disintegrate, and after twenty-
four hours scarcely an egg is left alive. If the eggs are left in the
acidulated sea water, they neither form a membrane nor segment. If
the eggs which have formed a membrane are put for from twenty-five
to fifty minutes into sea water whose concentration has been raised by
adding 15 c.c. 2\ n NaCl solution to 100 c.c. of sea water, the results
are surprising. Instead of a fraction of 1 per cent of the eggs develop-
ing, I had it in my power to cause 90 to 100 per cent of the eggs to
develop. All the eggs formed a membrane which is characteristic of the
egg fertilized with sperm. The rate of segmentation was practically the
same as that of the eggs of the same female fertilized with sperm.
A large percentage of the blastulae originating from this combination
of methods looked perfectly normal, and rose to the surface of the sea
* Loeb, University of California Publications, Physiology, Vol. I, pp. 83, 89, 113, 1904.
FER T I LIZ A T/OJV 1 69
water. Their further development into gastrulse and plutei occurred
with the same velocity as that of the control eggs, which had been fer-
tilized by sperm; and the larvae showed an equal degree of vitality.
It is an easy matter to produce and collect an unlimited number of plutei
from the eggs treated with this method.
When the eggs are taken out too early from the acidulated sea water,
they form no membrane, and the same is true when they remain too
long in the acidulated sea water. If eggs that have been treated with a
fatty acid without forming a membrane are submitted to the hypertonic
sea water for from twenty-five to fifty minutes, they will not develop into
larvae, and not even segment. It is therefore obvious that the membrane
formation and not the treatment with acid is responsible for these effects.
This is corroborated by some further observations.
O. and R. Hertwig discovered that if sea water is saturated with
chloroform — only traces of which are soluble in water — the unfertil-
ized eggs of the sea urchin form a membrane when put into this chloro-
form sea water.* Herbst found that benzol, toluol and creosote act
similarly.f It seemed to me that possibly hydrocarbons in general
might act in this way, and as a test I used amylene. It indeed called
forth the membrane formation. This method of calling forth a mem-
brane formation by hydrocarbons has a serious drawback, inasmuch as
the eggs show a tendency to undergo cytolysis, and are killed. By the
speedy transportation of the eggs into normal sea water some may be
saved.
It seemed of interest to ascertain whether it made any difference for
the parthenogenetic development which substance was used for the pro-
duction of the membrane. When the eggs were taken immediately after
the formation of the membrane from the sea water containing benzol,
not all the eggs that had formed a membrane underwent cytolysis.
When these eggs were subsequently treated in the way described above
with hypertonic sea water, they segmented, and some of them developed
into plutei. As long as the formation of a membrane is induced by a
substance which does not injure the egg too much, the subsequent short
exposure to hypertonic sea water may lead to the formation of an em-
bryo. In regard to their vitality, and possibly their structure, the em-
bryos may possibly differ according to the substance which is used for
the production of the membrane. This, however, must be determined
by further experiments.
It agrees further with the idea that the membrane formation and not
* O. and R. Hertwig, Untersuckungen zur Morphologie itnd Physiologie der Zdle, Heft
5, Jena, 1887.
f Herbst, Biologisches Centralblatt, Vol. 13, p. 14, 1893; and Mittheilungen aus d.
Zool. Station Neapel, Vol. 16, p. 445, 1904.
170 DYNAMICS OF LIVING MATTER
the acid effect is essential in these experiments, that not all the acids
can be used in these experiments. HN03, HC1, H2S04 and dibasic
or tribasic organic acids such as oxalic or citric, etc., could not
be used, while C02 called forth the membrane formation.
The order in which the two agencies are employed is not a matter
of indifference. When the eggs are first exposed to the above-mentioned
hypertonic sea water for about twenty to fifty minutes and then sub-
mitted to a process which calls forth the membrane formation (e.g. to
the treatment with fatty acid), the eggs form a membrane, but will
not develop into larvae. As a rule, they disintegrate within twenty-four
hours, and behave in every way as if they had been treated with the acid
alone. If one wishes to treat them with hypertonic sea water first, they
must remain in this solution for about from one and one half to two
hours. If after this time the membrane formation is called forth,
almost all the eggs develop, and a number of the larvae rise to the sur-
face. This method also gives good results.
If in eggs the membrane formation is called forth first, and if they
are subsequently exposed to the above-mentioned hypertonic sea water
for more than fifty minutes, either no egg develops or the development
is very abnormal.
All the facts mentioned in this and the previous communications
indicate that the process of membrane formation is an essential and
not a secondary phenomenon in this method of artificial partheno-
genesis.
Five years ago I ventured the suggestion that the process of
membrane formation is a process of coagulation. It is, however,
obvious that the membrane formation in these experiments cannot
be attributed to an acid coagulation, as in this case the membrane
formation should occur while the eggs are in the acid, and not after
they are taken out. Moreover, the fact that only certain acids act
in this way also excludes such an opinion. These facts suggested the
possibility that the fatty acids did not produce the membrane forma-
tion through the H-ion, but by the anion or the undissociated molecule,
and that, moreover, the H-ion directly antagonized the membrane
formation. This idea was tested and found correct. If a fatty acid is
added to benzol sea water, the eggs are no longer able to form a mem-
brane while they are in this mixture, though they form a membrane
while they are in benzol sea water which is free from fatty acid. From
a closer observation of the process of membrane formation I am in-
clined to believe that it is due to a process of secretion, i.e. the squeez-
ing out under pressure of a liquid from the interior of the egg.* I am
* Loeb, Pflugerh Archiv, Vol. 103, p. 257, 1904.
FERTILIZA T/OJV 1 7 1
no more able to state the nature of the forces which underlie secretion
in this than in any other case.
These experiments show that it is possible to completely imitate by
physicochemical means the effect of the spermatozoon upon the sea,
urchin egg. It is also obvious that this method is somewhat complicated
and specific, and that it cannot be well covered by the phrase that the
method consists in a "stimulation," for the word "stimulation " does not
— as far as I know — mean that we have to treat an organ first for one
ft
half minute with 50 c.c. of sea water + 3 c.c. — butyric acid and then
for from twenty-five to fifty minutes with a mixture of 100 c.c. of sea
water + 14 c.c. 2\ n NaCl solution. Moreover, these quantitative data
vary slightly for different species of sea urchins, e.g. Strongylocentrotus
purpuratus and Jranciscanus.
Yet some authors have maintained that any kind of stimulus, or
various chemical substances, might produce artificial parthenogenesis in
the egg of the sea urchin. These statements are based partly on mis-
understandings and partly on errors. In a former paper I stated that
it makes no difference how the osmotic pressure of the sea water is
raised, whether by sugar, by urea, or by salts; if the pressure is only
sufficiently high, the parthenogenetic development of the sea urchin's
egg will occur. Morgan makes use of this fact to attempt to show that
inasmuch as sugar as well as salts cause the development, various stimuli
can produce the development. He overlooks the fact that in this case
the sugar or salt does not act chemically, but solely osmotically by with-
drawing water from the egg, and that for this effect it is immaterial
what the chemical character of the dissolved substance is. Other
authors have been misled by mistaking parasitic larvae found in their
cultures for the larvae of sea urchins. Ariola has maintained that the
eggs of sea urchins develop normally parthenogenetically at Naples. I
may state that neither the unfertilized eggs of Arbacia nor those of
Strongylocentrotus of the Atlantic or the Pacific coast of America ever
develop, and that the same has been found for the eggs of the sea urchins
at Naples by all competent workers. Ariola has given a description
and drawings of the larvae he found which he considered as normally
parthenogenetic larvae of sea urchins, and I believe that they were prob-
ably larvae of some mollusk; they were certainly not the larvae of the
sea urchin. I mention this fact simply to show that unless an author
actually observes the origin of a larva from the egg, he may fall into
serious error. Viguier maintains that the sea urchins in Algiers are
naturally parthenogenetic. I should place more confidence in this
author's statements were they written in a more dispassionate, scien-
172 DYNAMICS OF LIVING MATTER
tific tone, and if his precautions against sources of error were more
adequate. Still, it is not impossible that some physical or chemical
condition accidentally present in Algiers may bring about effects
similar to the extraction of water from the eggs of these animals in this
country.
Since it is possible to fertilize the egg of the sea urchin and that of
the starfish by the spermatozoa of the latter species, it seemed also pos-
sible that the fertilization of the starfish's egg might be caused by the
same substances which cause the fertilization of the egg of the sea urchin.
I have made experiments on the egg of a form of Asterina which is com-
mon in the bay of Monterey.* This egg forms a membrane upon the en-
trance of a spermatozoon. I found that as in the case of the sea-urchin
egg, the egg of Asterina forms a membrane after having been treated with
a fatty acid. The only difference is that the egg of Asterina requires more
acid for this result than the egg of Strongylocentrotus. When the eggs of
Asterina had been put for about one and one half to two minutes into a
n
mixture of 50 c.c. sea water + 5 c.c. — acetic or butyric acid, they
formed a membrane when put back into normal sea water. When they
were put into 50 c.c. sea water 4- 1 c.c. benzol or amylene, they formed
a membrane while they were in this mixture.
Eggs in which this membrane formation had been called forth were
able to develop into normal larvae, and the development of such eggs
resembled in rapidity and the form of the larvae completely that pro-
duced by sperm.
The egg of the starfish is, as a rule, not mature when it leaves the
ovary. It possesses a large nucleus, and the process of maturation con-
sists in the nucleus being dissolved in the protoplasm of the egg and the
polar bodies being thrown out. As long as the large nucleus is visible
in the egg it cannot be fertilized by a spermatozoon, nor can its develop-
ment be called forth by a treatment with one of the fatty acids or with
one of the hydrocarbons, like benzol or amylene. Not until the nucleus
has become dissolved in the protoplasm can a spermatozoon fertilize the
egg, and at about the same time it becomes possible to produce artifi-
cially a membrane formation and development.
There is a noticeable difference in the method by which the starfish egg
can be caused to develop and the method which is necessary in the case
of the sea-urchin egg. For the former the process of artificial mem-
brane formation is sufficient, while the sea-urchin egg has, in addition,
to be submitted for a short time to the action of hypertonic sea water.
This difference is rendered a little more comprehensible by the fact that
* Loeb, University of California Publications, Physiology, Vol. 2, p. 147, 1905.
FERTILIZA TIO AT 1 73
a small percentage of the eggs of the starfish are able to develop without
any external cause or agency being applied. The number of these eggs
varies in the eggs of different individuals, but is, as a rule, very small,
e.g. a fraction of 1 per cent. The rate of segmentation in these "natu-
rally" parthenogenetic eggs is slower than the rate of development of
the eggs fertilized by sperm, and the blastula begins to swim consid-
erably later than the blastulae coming from fertilized eggs or from eggs
in which a membrane had been produced artificially. Moreover, the
blastulae of the spontaneously developing eggs differ somewhat in ap-
pearance from the blastulae coming from the two latter.
Neilson and I found that the number of eggs which develop without
a membrane formation can be increased by treating the eggs transitorily
with acidulated sea water. Delage* simultaneously obtained the same
result by treating the eggs of Asterias with C02 ; I am inclined to be-
lieve that the C02 acts as an acid, although Delage is not willing to admit
this.
The fact that the unfertilized eggs of the starfish may develop with-
out any external cause has often been overlooked, and this has led some
authors again to state that any "stimulus" may cause the development
of this egg. Acids, indeed, increase the number of eggs which will
develop; the same is possibly true for mechanical agitation, as A. P.
Mathews has observed. f He is inclined to believe that in this case the
mechanical agitation is the direct cause of development (by producing
coagulation). It is, however, necessary to state that the taking up and
dropping of eggs with a pipette suffices. In eggs of Amphitrite, an
Annelid, I have convinced myself that the number of eggs which develop
does not bear any relation to the extent of the mechanical agitation. I
consider it possible that some secondary factor connected with the agi-
tation, such as the diffusion of gases into or from the egg, e.g. C02, may
be the real factor involved in this case.
The experiments thus far mentioned indicate that the process of
membrane formation, or some process underlying this, is of importance
for the complete physicochemical imitation of the developmental in-
fluence of the spermatozoon. The question arises, What is the nature
of this process? It seems to me from my observations on Echino-
derms that the essential feature of this process is the squeezing out
under pressure or the secretion of a fluid from the protoplasm of the
egg. As a mechanical effect, the surface film of the egg is lifted and
separated from the protoplasm by a liquid secreted by the egg. When
the secretion of this liquid occurs very slowly, the lifting up of the sur-
* Delage, Archiv. de Zool. exp'erimtntale, Vol. 10, p. 213.
t A. P. Mathews, Am. Jour. Physiology, Vol. 6, p. 142, 1901.
174 DYNAMICS OF LIVING MATTER
face film will not occur; only when the secretion of the liquid is rapid
enough will the secretion result in the membrane formation. According
to this view, the secretion of a liquid from the egg is the essential feature,
while the membrane formation itself is possibly only a secondary, mechan-
ical effect of the sudden secretion. If this be true, the essential feature
in fertilization in Echinoderms is not the membrane formation itself, but
the secretion of a liquid from the interior of the egg. This conception
is corroborated by an observation I made several years ago. I found
that the unfertilized eggs of a sea urchin could be kept alive in sterilized
sea water for a week, or possibly more. When sperm was added to
such eggs, they developed, but without the formation of membranes. It
is quite possible that a process of secretion may be produced in every
egg through the entrance of a spermatozoon, while the actual separation
of the surface film of the egg from the protoplasm is only a secondary
mechanical consequence of this secretion, which may or may not occur.
Since I have only recently recognized the importance of the process
of membrane formation for the complete physicochemical imitation of the
developmental effect of the spermatozoon, I have not yet found time to
see whether it holds good only for Echinoderms. An observation re-
cently made by Professor Lefevre on artificial parthenogenesis in a
marine worm, seems to indicate that the artificial membrane formation,
or rather the process underlying it, is of more general importance.
Lefevre found that about 50 per cent of the eggs of Thalassema develop
into normal larvae, after having been exposed to sea water (to which a
little acid had been added) for a few minutes. After' they were taken
out of the acidulated sea water, they formed a membrane and developed.
The case seems to be similar to that of Asterina. The development of
the eggs seemed to be normal, and the vitality of the larvae seemed to
be the same as that of the larvae originating from fertilized eggs. I, as
well as others, had, before Lefevre's observations, produced artificial
parthenogenesis in the eggs of worms, but without artificial mem-
brane formation. In all these cases the larvae had always a diminished
vitality, and the development was often different from that of the egg
fertilized by sperm. I had found that the unfertilized eggs of Chcetopte-
rus, a marine Annelid, can be caused to develop into swimming larvae*
with certainty by adding a small but definite amount of a soluble potas-
sium salt ; but the vitality of these eggs was considerably less than that
of the larvae originating from fertilized eggs. I may also add — although
this does not belong to our problem — that I noticed that the eggs of
Chatopterus, which had been caused to develop parthenogenetically by
KC1, reached the trochophore stage and began to swim about seem-
* Loeb, Am. Jour, Physiology, Vol. 4, p. 423, 1901.
FERTILIZA TION 1 7 5
ingly without segmenting. Frank Lillie* afterward examined such
eggs histologically and convinced himself indeed that such is the case.
Bullotf produced a much more normal type of development in the un-
fertilized eggs of another Annelid, Ophelia, by submitting these eggs
for about two hours to hypertonic sea water. In this case the segmen-
tation was normal and the larvae formed were also normal, but they
only lived two days. It will therefore be of interest to find out whether
in Chcetopterus the same means which in Echinoderms lead to a mem-
brane formation are able to induce a parthenogenetic development
which resembles in all its features the development caused by a
spermatozoon.
Kostanecki | found that by a treatment with hypertonic sea water,
the unfertilized eggs of a Mollusk (Mactra) could be caused to undergo
the first segmentations; and I found afterward § that this method led
in other Mollusks (Lottia, Acmcea) to the production of swimming larvae.
I have recently tried my new method on the eggs of Lottia gigantea.
It seems that the combination of the treatment with fatty acid and
hypertonic sea water gives better results than the osmotic treatment
alone. Some attempts have been made to cause the eggs of vertebrates
to develop parthenogenetically. Bataillon|| has shown that the unfer-
tilized eggs of the frog and of Petromyzon can be caused to segment as
far as the morula stage by putting them for some time into a salt solu-
tion of a certain concentration, whereby they lose water.
It was natural to try whether or not substances can be extracted
from the spermatozoon which cause the unfertilized egg to develop.
Pieri made the statement that this could be done, but he evidently worked
with sea water contaminated by spermatozoa. After the appearance
of my first paper, H. Winkler made experiments with the extract of
spermatozoa of sea urchins which, according to his description, caused
the eggs of the same species to go through the first stages of segmenta-
tion; If no larvae, however, developed from these eggs. These experi-
ments were repeated by Gies, who tried to ascertain whether or not an
enzyme could be obtained from the spermatozoon which caused the
unfertilized egg to develop; but the results were absolutely negative.
Not a trace of segmentation could be produced in eggs treated with such
extracts. These results contradict the conclusions of Winkler.** I am
inclined to believe that Winkler worked with sea water whose concen-
* F. Lillie, Archiv filr Entwickelungsmechanik, Vol. 14, p. 477, 1902.
f Bullot, Archiv fur Entwickelungsmechanik, Vol. 18, p. 161, 1904.
J Kostanecki, Bulle. Acadhnie de Sciences, Krakau, 1902.
§ Loeb, University of California Publications, Physiology, Vol. 1, p. 7, 1903.
|| Bataillon, Archiv filr Entwickelungsmechanik, Vol. 18, 1904.
If Hans Winkler, Nachrichten der Gesellsch. der Wissenschaften zu Gottingen, p. 87, 1 900.
** Gies, Am. Jour. Physiology, Vol. 6, p. 53, 1901.
176 DYNAMICS OF LIVING MATTER
tration had been slightly raised, or which had been rendered slightly
alkaline through evaporation. In either case results such as he produced
may be observed.
Max Cremer also obtained absolutely negative results when he
tried to cause the development of fish eggs with extracts obtained from
the sperm of the same species with the Buchner press.
We may finally raise the question whether we can form, on the basis
of the facts mentioned, any idea as to how the spermatozoon causes the
egg to develop. From the facts stated in our fourth lecture in regard
to cell division it is obvious that the essential effect of the spermatozoon
consists in the transformation of part of the protoplasmic or reserve
material in the egg into the specific nuclein or chromatin substance of
the nucleus. In each nuclear division one half of the mass of each
original chromosome goes into the nucleus of each of the two resulting
cells. But during the resting period which elapses until these nuclei
are ready to divide again, each chromosome grows to its original size
again, and then a new division occurs. It is quite possible that the
oxygen which is required for the process of cell division is needed for
the synthesis of nuclein or chromatin substance. The fact that
the rate of development is influenced by temperature in much the
same way as are chemical reactions supports the idea given above
that the essential feature of fertilization consists in the starting or the
acceleration of a chemical reaction which is going on steadily in
the egg.
It was natural to think first of the possibility that the spermatozoon
carries a positive catalyzer into the egg, and thus accelerates the above-
mentioned synthetical process, which might also occur in the unferti-
lized egg but too slowly to lead to any development. It occurred to me
that if this idea were correct the unfertilized eggs of the sea urchin might
segment in normal sea water if they only could be kept alive for a suffi-
cient length of time. In order to test this idea I took out the ovaries with
bacteriological precautions and kept the eggs alive in sterile sea water
for a week. Not an egg segmented, but when sperm was added, seg-
mentation occurred promptly. This observation did certainly not
support my idea of the spermatozoon carrying a positive catalyzer into
the egg. It then occurred to me that a rise in temperature should act
like a spermatozoon, since a rise in temperature should accelerate the
velocity of chemical reactions. While a rise in temperature promptly
accelerates the development after the egg is fertilized, or caused to de-
velop by physicochemical methods, I have thus far not been able to start
development in this way.
It then occurred to me that a superposition of two methods of fer-
FERTILIZATION \ 77
tilization should lead to an acceleration of a process of development,
if it were true that the nature of fertilization consisted in a positive cataly-
sis. I combined fertilization by sperm, osmotic fertilization, and the
new method of fertilization in all possible ways in the egg of Stron-
gylocentrotus without, however, being able to accelerate the process
of development; on the contrary, as a rule, the process of development
was markedly retarded. The idea that the spermatozoon carries a
positive catalyzer into the egg has, therefore, thus far not received any
support.
A second possibility which was to be considered was that the sper-
matozoon removes from the egg somehow a negative catalyzer or a condi-
tion whose presence in the egg prevents the development of the latter. If
this were the case, we could readily understand why a rise in temperature
which accelerates the development in the fertilized egg cannot — as far
as my present knowledge goes — start the process of development in
the unfertilized egg. We can, moreover, well understand why a process
of secretion which seems to underlie the membrane formation may be
of such great importance for the process of development. Finally, we
may be able to understand a fact which I have observed in the eggs of
starfish, and which has not yet been mentioned. When the eggs of
Asterina or Asierias are allowed to ripen, they will die within a few hours
unless they develop either spontaneously or through the influence of
sperm or some of the above-mentioned agencies.* The disintegration
which leads to the death of the nondeveloping egg is obviously due to
an oxidation, since I found that the same eggs when kept in the absence
of oxygen will not disintegrate. We know that oxygen is an absolute
prerequisite for the development of the fertilized egg. The fact that
oxygen is a poison for the mature but nondeveloping egg shows that
altogether different chemical processes must occur in the unfertilized,
nondeveloping and the developing egg of the starfish. The process of
fertilization seems, therefore, to consist in the elimination or alteration
of a chemical condition in the egg, and that this alteration makes the
processes of synthesis of nuclein material from the protoplasm possible.
In my first experiments on artificial parthenogenesis I was inclined
to believe that the immediate effect of the methods employed consisted
in a modification of the condition of the colloids in the egg. This view
is contradicted by my recent experiments. When the process of arti-
ficial membrane formation is produced in the egg of a sea urchin, the
egg does not show the changes leading to a cell division, e.g. the forma-
tion of astrospheres, until after one or two hours. But even this does not
* Loeb, Pfluger's Archiv, Vol. 93, p. 59, 1902. University of California Publications,
Physiology, Vol. 2, p. 147, 1905.
178 DYNAMICS OF LIVING MATTER
lead to the development of the egg unless the egg has been submitted
for twenty minutes to the hypertonic sea water. It is therefore obvious
that the process of astrosphere formation or similar alterations cannot
be the direct effect of the act of fertilization and, moreover, it cannot be
the essential feature of it. I am inclined to believe that the direct and
essential effect of the spermatozoon and the methods of artificial par-
thenogenesis is the starting of a definite chemical process, and that the
formation of astrospheres is only a secondary effect of this.
It is in harmony with this idea that the process of segmentation in
the case of artificial parthenogenesis is entirely regular, and does not
differ from that of fertilized eggs, provided that the right concentration
and time of exposure are selected.
I have not entered into a discussion of the cytological changes which
are noticeable in an egg in which artificial parthenogenesis has been
produced, and refer the reader to a masterly paper * by E. B. Wilson on
this subject.
* E. B. Wilson, Archiv fur Enttvickelungsmechanik, Vol. 12, p. 552, 1901.
LECTURE X
HEREDITY
i. The Hereditary Effects of the Spermatozoon and Egg
In addition to the developmental effects, the spermatozoon has a
hereditary effect, inasmuch as it transmits the paternal qualities to the
offspring. The experiments on artificial parthenogenesis or chemical
fertilization suggest the possibility that the developmental and the heredi-
tary agencies in the spermatozoon are connected with different substances.
O. Hertwig twenty years ago defined the process of fertilization as the
fusion of two nuclei; namely, the egg nucleus and the sperm nucleus.
While this fusion is apparently of importance for the hereditary effects,
one fails to see how a fusion of two nuclei must cause an egg to develop.
The experiments on artificial parthenogenesis indicate clearly enough
that the development of the egg can be caused without even the presence
of a sperm nucleus. On the other hand, the experiments on merogony
show that a fragment of egg protoplasm which has no nucleus can
develop when fertilized by a spermatozoon. Delage made extensive
experiments in which he cut pieces of protoplasm from the egg of
Echinoderms, Annelids, and Mollusks.* These pieces developed when
a spermatozoon entered into them. In this case fertilization occurred
without a fusion of nuclei, as there was no egg nucleus present.
It is a very striking fact that for the first stages of development the
hereditary influences of the spermatozoon and the egg are by no means
equal. It seems that for these first stages the influence of the egg by
far exceeds that of the spermatozoon. It may almost be said that
the first stages of the embryo are exclusively or almost exclusively
determined by the egg, and not by the spermatozoon. This is best
illustrated if we hybridize forms whose first stages of development differ
radically from each other, e.g. sea urchin and starfish. The pure larvae
of both forms go through a blastula and gastrula stage, but then their
development becomes strikingly different, inasmuch as the sea urchin
larva develops into a pluteus with a skeleton, while the starfish larva
* Delage, Archives de Zoologie experimentale, Vol. 7, p. 383, 1899.
179
180 DYNAMICS OF LIVING MATTER
forms no skeleton. If the egg of a sea urchin is fertilized by the sperm
of a starfish, those larvae that live long enough develop invariably into a
pluteus.* It would be interesting to ascertain whether the hybrid
larvae produced from a starfish egg by the fertilization with a sea urchin
spermatozoon ever form a pluteus larva. These data also indicate
that the statement that fertilization consists in the fusion of two nuclei
does not cover all the facts.
As far as the adult is concerned, it seems that, as a rule, spermato-
zoon and egg have an equal share in the transmission of the hereditary
qualities. Mendel states that in the case of the hybridization of two
species of peas, a and b, the results were the same, whether the pollen came
from the species a and the egg from the species b, or vice versa. We
shall see later on that the early embryo is to a certain extent predeter-
mined in the protoplasm of the egg. This makes it natural that these
early stages should depend upon the egg, and not upon the spermato-
zoon. As far as the adult is concerned, the protoplasm has to be formed
by the taking up of food, and the chemical as well as the subsequent
physical changes which the material undergoes will be under the in-
fluence of the catalytic agencies of both the egg and the spermatozoon.
We do not know which circumstances in the sexual cells determine
the hereditary effects, although one would naturally think first of definite
chemical compounds as the bearers of hereditary qualities. The greater
part of the spermatozoon, namely, the head, consists of a salt whose
acid is nucleinic acid, whose base in some fishes and starfish is pro-
tamine, in other forms histones, which latter, however, are closely related
to the protamines. In order to decide whether the nucleins or the
histones or the protamines are of importance for the hereditary qualities,
it would be necessary to decide whether the nuclei of the eggs of one
form contain always the same base as that found in the sperm of the
same species. This should be expected from the fact that the hereditary
influence of egg and sperm is equal in the adult offspring, at least.
It seems that the base is not always identical in the egg and sper-
matozoon of the same species, and this seems to indicate that the
nucleic acid is of more importance for heredity than protamines and
histones. Aside from the nuclein we find albumin and globulin, es-
pecially in the tail, and in the latter also lecithin, cholesterin, and fat.
Miescher believed that in the head of the spermatozoon an iron compound
exists. It is impossible to draw any far-reaching inference concerning
the nature of the substances which transmit hereditary qualities from
these meager data.
The fact that the spermatozoon contributes just as much to the trans-
* Loeb, loc. cit.
HEREDITY l8l
mission of hereditary qualities in the adult as the egg, although the mass
of the latter is, as a rule, many times larger than that of the spermato-
zoon, makes it certain that only a small fraction of the contents of the
egg has anything to do with this transmission of hereditary qualities.
Since the head seems to be the more important part of the spermatozoon
for the process of heredity, and this head is a homologue of the egg
nucleus, Boveri expressed the idea that the nucleus, and not the proto-
plasm, is the really significant part of the egg in matters of heredity.
In order to test this idea he undertook a very ingenious experiment;
namely, the fertilization of an enucleated fragment of the egg of one
species of the sea urchin by the sperm of another species. If his view
were correct, such a hybridization should produce a larva with purely
paternal characteristics, as the egg only furnished the protoplasm which
was not expected to influence the hereditary qualities. The execution
of this experiment is extremely difficult. Boveri is inclined to believe
that, according to the experiments carried out so far, the fertilization
of enucleated fragments of eggs of Sphcer echinus by the sperm of Echi-
nus yields plutei of a pure type of Echinus, although he does not consider
the question as definitely settled.* I am inclined to believe that in the
early stages the paternal influence would, at the best, be very slight.
The egg protoplasm contains more or less reserve material which is
only gradually transformed into the characteristic compounds of the
embryo. It is therefore obvious enough that at first the embryo must
show effects of this relation. When the protoplasm of the egg possesses
a striking pigment, the larva will possess the same for some time at
least ; if such an egg is hybridized with the sperm of a form whose egg
is unpigmented, the larva will, of course, possess a "maternal" quality
which is due solely to the protoplasm (Driesch). In the eggs of birds
the incubation period depends ceteris paribus upon the mass of yolk.
When a species with a long incubation period is crossed with one of a
short incubation period, the egg, and not the sperm, determines the
incubation period, as Whitman observed in pigeons. It is obvious,
then, that during the first stages of development an influence of the
protoplasm upon heredity may make itself felt, which will disappear as
soon as the protoplasm of the egg has been transformed into the tissues
of the embryo: It does not seem to me that a discussion as to the rela-
tive influence of protoplasm and nucleus upon heredity will prove
very fertile, but that it is necessary to transfer this problem as soon as
possible from the field of histology to that of chemistry or physical
chemistry. This view is supported by investigations concerning the
toxic effects of blood of one form upon not too closely related forms.
* Boveri, Archiv fur Entwickelungsmechanik, Vol. 2, p. 394, 1896.
1 82 DYNAMICS OF LIVING MATTER
Until about thirty years ago the idea was held generally that a trans-
fusion of the blood of an animal into the veins of a human being was
permissible or advisable in the case of severe loss of blood. We know
to-day that in such cases physiological salt solutions or human blood
must be injected, and that the blood of animals is generally toxic. This
important discovery was made by Landois,* who showed that blood of a
foreign species generally destroys the red corpuscles of the animal into
which it is infused. He investigated systematically the destructive
force of foreign blood upon the red corpuscles of various animals, and
made the remarkable discovery that there exists a striking relation be-
tween this effect and the blood relationship of animals. I will quote
the summary of this part of his investigation: "My results include a
point which is of importance for the systematic order of animals;
namely, that those animals which are closest to each other in regard to
their anatomical qualities also possess the most homogeneous blood,
inasmuch as a transfusion of blood between two closely related animals
brings about the least rapid destruction of the foreign blood. The
transfusion thus offers us a means of determining in questionable cases
the relationship of animals. A transfusion of blood is possible between
varieties of the same species ; the blood of species that are very close to
each other shows hemolysis only very gradually, and the animals with-
stand large quantities of foreign blood; the more distant, however,
animals are, the more violent the effects of the foreign blood become "
(p. 289). The hemolysis consists in the red blood corpuscles becoming
permeable for the hemoglobin they contain, which begins to diffuse
out. The red blood corpuscles become in consequence pale (ghosts or
shadows). It is obvious that this diffusion of the hemoglobin is rendered
possible through some chemical alteration of the blood corpuscle. The
experiments of Landois prove that the blood of closely related species
is chemically and physicochemically more nearly identical than the
blood of more distant forms. More recently the observations of Landois
were taken up by Friedenthal,! Gruenbaum, and Nuttall. $ These
experimenters were able to avail themselves of Bordet's precipitation
method. Bordet had found that after serum of a foreign species has
repeatedly been injected into a rabbit, a precipitation will occur when
blood of that foreign species and the blood of this rabbit are mixed.
Moreover, the same reaction occurs when blood from an animal related
to the one whose serum had been injected is mixed with the blood of
the rabbit. Friedenthal and Nuttall used this reaction to find out the
* Landois, Die Transfusion des Blutes, Leipzig, 1875.
f Friedenthal, Engelmann's Archiv, p. 494, 1901 ; and Berliner klinisch-therapeup-
tische IVochenschrift, 1904.
t G. Nuttall, Blood Immunity and Blood Relationship, Cambridge, 1904.
HEREDITY 1 83
blood relationship of animals. Nuttall found among others that if
dog's serum was injected into a rabbit, the serum of this rabbit after-
ward gave a precipitation with the blood of eight various canides,
but with the blood of no other group of animals ! These experiments
may also explain why the bastards between the sea urchin and starfish
show a much greater mortality than the pure breed. In my experi-
ments the hybrids between starfish and sea urchin died in large
numbers after they reached the blastula or gastrula stage.* It seems as
if the spermatozoon of the starfish, in addition to a developmental sub-
stance, also carries something else into the sea urchin's egg which poisons
the latter. It remains for further experiments to decide how far the
physicochemical incompatibility of heterogeneous species which Landois
and his successors discovered, restricts heterogeneous hybridization. It
is, however, already obvious enough that ultimately the problem of
hybridization and heredity must be transferred from the morphological
to the chemical or physicochemical field.
We may now continue the discussion of the problem of heredity.
The man whose work marks with that of Landois the beginning of a
real theory of heredity had a fate similar to that of Landois. Gregor
Mendel was a teacher of physics in Graz, and evidently the writings of
Darwin induced him to investigate the laws of heredity ; but he went
at the problem in a spirit so entirely different from that of the biologists,
and at the same time in a way which was so superior, that his discoveries
were entirely overlooked for over thirty years, until De Vries discovered
the same facts, and also discovered accidentally Mendel's paper. At
almost the same time Correns and Tschermak also called attention to
Mendel's work. Mendel f carried on experiments on the hybridization
of varieties of peas which he selected so that they differed in only one
characteristic. It was his intention to find out what became of that
discriminating or critical characteristic in the offspring. He found that
the children of such parents — the first generation of hybrids — did
not occupy an intermediate position between the two parents in regard
to the discriminating characteristic, but were all pure breeds, inasmuch
as the discriminating characteristic of one parent was transmitted to
all of the children, while the characteristic of the other parent was ap-
parently not transmitted. The discriminating characteristic of the peas
used by Mendel for his experiments were, e.g., the difference in the shape
of the ripe seeds, whether they were spherical or angular. When he
crossed two forms of peas which were identical in every respect, except
* Loeb, loc. cit.
t Gregor Mendel, Versuche ilber Pflanzenhybride. Ostwald, Klassiker der Naturwissen-
schaften, Vol. 121. De Vries, Die Mutalionstheorie, Leipzig, 1901.
1 84 DYNAMICS OF LIVING MATTER
that the shape of one parent was angular that of the other round, all
the children or hybrids of the first generation had round seeds. It
was immaterial whether the female or the male was of the round seed
variety. If we now assume, as we must, that there is also a corre-
sponding difference in the sexual cells of the round seed variety and the
angular seed variety, we must assume that in the mixing of the two the
determinants of the round shape of the seed dominated, while the de-
terminants for the angular shape of the seeds were prevented from
manifesting themselves.
In another set of experiments Mendel crossed two varieties which
were alike in every respect except the coloration of the albumin of the
seed (endosperm). In one variety this possessed a pale yellow color,
in the other it was green. The children of two such parents possessed
only yellow endosperm.
In a third case the discriminating characteristic between the two
parents was the color of the shell of the seed : one was white, the other
gray or grayish brown. The former also had white blossoms, the latter
violet blossoms. The children all had seeds with gray shells and violet
blossoms.
It is therefore obvious that in these cases one characteristic dominated,
and Mendel called this the dominating characteristic, while the other,
which was suppressed in the first generation of children, he called the
recessive characteristic. Thus the spherical shape of the seed is a domi-
nating, the angular shape a recessive, characteristic.
The first generation of hybrids was therefore in regard to the dis-
criminating characteristic not distinguishable from the pure breed of
the one parent, which possessed the dominating characteristic; yet it
was different in one respect, namely, its sexual cells. The child of
two parents, the one of which possessed angular, the other spherical
seeds, possessed two kinds of sexual cells in about equal number;
namely, one half being cells possessing the determinant for the dominant,
the other possessing the determinant for the recessive, characteristic.
This follows from the results of Mendel's experiments when he crossed
the hybrids of the first generation among themselves. In this case
there was no uniform offspring, but the two distinct types, one with the
recessive and one with the dominating characteristic, now reappeared.
Only a fraction of the hybrids of the second generation had the dominant
characteristic, the rest had the recessive characteristic. When the number
of the individuals used for experimentation was sufficiently large, there
existed always a definite ratio between the two kinds of offspring : the
number of hybrids with the recessive characteristic was always one
third of those with the dominating characteristic. This is exactly what
HEREDITY 1 85
we should expect if the hybrids of the first generation possessed two
kinds of sexual products in equal numbers; namely, those of the
paternal and those of the maternal species or variety. If a large number
of individuals of this kind be crossed, according to the law of probability,
in one fourth of the cases an egg cell with the determinant for the reces-
sive characteristic and a pollen cell of the same type would meet. This
would result in pure offspring with the recessive characteristic. In one
fourth of the cases egg cells with the determinant of the dominating
characteristic would meet with the pollen of the same type, and the re-
sult would be pure offspring with the dominant characteristic. In one
fourth of the cases an egg cell with the determinant for the dominant
characteristic would be met by pollen cells with the determinant for the
recessive characteristic, and this would give rise to individuals with the
dominant characteristic ; in the last fourth of the cases an egg cell with
the determinant for the recessive characteristic would be met by pollen
with the determinant for the dominant characteristic, and this again
would give offspring with the dominant characteristic. In this way
three fourths of the total offspring in the second generation would have
the appearance of the species or variety with the dominant, and one
fourth of the total offspring would have the appearance of the species
with the recessive, characteristic; both kinds would therefore be in the
numerical relation of one to three, as stated.
Through many cultures, Mendel has shown that his conclusions are
correct. Thus, e.g., his theory demanded that if the last-mentioned
experiment be continued, and the individuals of the first-mentioned
fourth of the offspring, namely, the ones that have reverted to the
recessive character, be bred among themselves, only pure breeds with
recessive character should be produced. The experiments proved that
this is entirely correct.
Mendel raised also the question as to what would happen if varieties
of peas which differ in regard to two or more characteristics should
be hybridized. In this case, the hybrids of the first, as well as of the
later, generations behaved as if a specific hereditary substance existed
for each characteristic, and as if these substances did not influence each
other. For each one of the discriminating characteristics, the same laws
hold which existed where the varieties differed only in regard to one
characteristic.
The epoch-making importance of Mendel's work lies in the fact that
he, for the first time, gave not a hypothesis but a theory of heredity,
which made it possible to predict the results of hybridizations numeri-
cally. His work forms the basis for all further work in this field which
is of equal theoretical and practical importance.
1 86 DYNAMICS OF LIVING MATTER
The observations of Mendel have since been confirmed and enlarged
upon. Not only botanists like De Vries, who independently rediscovered
Mendel's laws, but also zoologists like Bateson and his pupils, Cuenot,
Castle,. Guyer, and many others, have added to this field.
Mendel's laws do not, however, include all the cases of hybridization.
De Vries has investigated this field in a masterful way, and has shown
that there are at least two types of hybridizations : one in which, as in
Mendel's cases, a separation of the discriminating characteristics occurs
again in the offspring, and another in which constant races are at once
produced. This type of hybridization is the one which proves especially
useful to plant breeders in their attempts to produce new varieties.
De Vries believes that the latter type of hybrids is produced when the
sexual cells of one parent have a determinant for which there is no cor-
responding determinant in the sexual cells of the other parent.
The objection might be raised that such a theory of chemical deter-
minants in the sex cells as the cause of heredity might find difficulty
in explaining the heredity of instincts; I believe that the contrary is
the case. In a paper on "Egg Structure and the Heredity of Instincts" *
I have pointed out that the hereditary character of the instincts demands
a chemical rather than a morphological theory of heredity. Many
instincts are obviously the outcome of tropisms. For the transmission
of an instinct based on heliotropism, all that is required is the presence
in the sexual cells of photosensitive material, or of a substance from
which such material can be formed.
The current morphological and cytological literature contains many
attempts at explaining the phenomena of heredity on a purely morpho-
logical or cytological basis. There is no objection to this, as long
as we realize that the morphological structures can only play a role
through their physical and chemical properties.
0
2. The Determination of Sex and the Secondary Sexual
Characters
Several years ago an embryologist published the hypothesis that sex
could be determined by submitting the mother to a certain diet. Delage
pointed out that this idea was contradicted by the fact that in about
30 per cent of the cases twins have different sex, which would be
impossible if the diet of the mother determined the sex of the offspring.
There is, however, one condition under which twins have invariably
the same sex ; namely, when they come from the same egg. We have
seen in a former lecture that from one egg twins can arise; namely,
* Loeb, The Monist, 1897.
HEREDITY 1 87
when the contents of the egg are cut in two during the early periods of
development, e.g. when the first two cleavage spheres become separated
from each other. In the case of mammalian or human twins, we possess
a criterion for the fact whether they come from one or two eggs in the
condition of the egg membranes. Twins coming from different eggs
have as a rule separate chorions. This follows from the development
of the chorion. In all cases where twins have a common chorion they
have also identical sex. This indicates that the sex of the embryos was
determined before the germ was split into two parts, and as this must
occur in the earliest stages of development, it follows that the sex of an
embryo is definitely determined very early; how early can only be
guessed at in mammalians, but in certain lower forms it can be shown
that the sex is already p reestablished in the egg before the egg is even
fertilized.
A striking example for this assertion was discovered by Korschelt
in Dinophilus apatris, a worm of the group of Turbellarians. As
Korschelt's paper is not accessible to me, I quote the observation after
Lenhossek.* Dinophilus lays two kinds of eggs, the one large and
opaque, the other small and transparent. The eggs are fertilized inside
the body of the female, and are afterward deposited in the sea water.
Korschelt separated the two types of eggs, and found that the large
opaque eggs give rise to females, the small transparent eggs to males.
If this observation is correct, there can be no doubt left that in this case
sex is already determined in the egg before the egg is fertilized.
Facts of a somewhat analogous character seem to exist in a number
of forms such as plant lice, Cladocera and Rotifers. The Aphides are
viviparous as long as the temperature is not too low and the plant is
not drying out. Under such conditions they give rise to offspring of one
sex only, namely, females. These reproduce females parthenogeneti-
cally which possess no receptacle. When the plant dries out, or the
temperature becomes low, in addition to females, males are also produced.
The females which originate at this time possess a receptacle, and hence
can pair. After pairing they are not viviparous, but lay fertilized eggs,
the so-called winter eggs. From such eggs parthenogenetic females
invariably arise, and now the cycle may be repeated. It is obvious that
at least the sex of the winter egg is determined as soon as it is formed.
The same is probably true also for the sex of the embryo which pro-
ceeds from the summer eggs. In Cladocera conditions are not very
different. From the winter egg females invariably arise, and these
give rise parthenogenetically to females until, under conditions which
have not been sufficiently investigated, males and females are formed,
* Lenhossek, Das Problem der geschlechtsbesti??imenden Ursachen, Jena, 1903.
1 88 DYNAMICS OF LIVING MATTER
which copulate. As in Aphides, only a definite type of eggs, the so-
called winter eggs, require fertilization, and from the fertilized eggs a
female originates in every case. In Rotifers also the winter eggs are
said to require fertilization and give rise to females.
We have already mentioned the fact that in bees the unfertilized
eggs give rise almost, or quite exclusively to males, while females
can only (or perhaps mainly) arise from fertilized eggs. This seems to
indicate that the entrance of a spermatozoon may give the egg a female
character, while without it, it has a male character. Lenhossek believes
it is possible that in bees, as perhaps in most animals, two kinds of eggs
exist, one for each sex ; that for some reason the male egg is not fertilized
when it is laid, while the female is fertilized. It is, however, difficult
to harmonize with such a view the fact that old queens, whose supply of
sperm in the receptacle is exhausted, and virgin queens lay only male
eggs.
Among certain insects, e.g. the Hemiptera and Orthoptera, two
kinds of spermatozoa have been found, but one kind of eggs. These
two kinds of spermatozoa differ in regard to a single chromosome, which
is found only in one half of the spermatozoa, while it is lacking in the
other ; or which is larger in one half of the spermatozoa than in the
other half.
The first one to recognize the existence of two kinds of spermatozoa
was Henking, who stated that in Pyrrhocoris (a Hemipteron) one half
of the spermatozoa of each male possessed a nucleolus while the
other half did not. Montgomery afterwards showed ■ that Henking's
nucleolus was an accessory chromosome. To McClung * of the Uni-
versity of Kansas belongs the credit of having first recognized the
importance of this fact for the problem of sex determination. He
observed an accessory chromosome in one half of the spermatozoa of
two forms of Orthoptera, Brachystola and Hippiscus, and traced their
history. His conclusion may be quoted in full: "A most significant
fact, and one upon which almost all investigators are united in opinion,
is that the element is apportioned to but one half of the spermatozoa.
Assuming it to be true that the chromatin is the important part of the
cell in the matter of heredity, then it follows that we have two kinds
of spermatozoa that differ from each other in a vital matter. We
expect, therefore, to find in the offspring two sorts of individuals in
approximately equal numbers, under normal conditions, that exhibit
marked differences in structure. A careful consideration will suggest
that nothing but sexual characters thus divides the members of a species
* C. E. McClung. The Accessory Chromosome — Sex Determinant ? Biological Bul-
letin, Vol. 3, p. 43, 1902.
HEREDITY 1 89
into two well-defined groups, and we are logically forced to the con-
clusion that the peculiar chromosome has some bearing upon the
arrangement.
"I must here also point out a fact that does not seem to have the
recognition it deserves ; viz. that if there is a cross division of the chro-
mosomes in the maturation mitoses, there must be two kinds of sper-
matozoa regardless of the presence of the accessory chromosome. It
is thus possible that even in the absence of any specialized element
a preponderant maleness would attach to one half of the spermatozoa,
due to the 'qualitative division of the tetrads'"*
McClung was inclined to believe that that half of the spermatozoa
which contains the accessory chromosome gives rise to male offspring,
while the other half gives rise to female offspring.
E. B. Wilson f has recently investigated the chromosomes of the
sex cells in a number of Hemiptera, and ascertained that the occur-
rence of two kinds of spermatozoa is a constant phenomenon in this
group. While in some forms the two kinds differ by an accessory chro-
mosome occurring in one half of the spermatozoa of a male, in other
forms they differ in regard to the size of one of their chromosomes.
In the latter forms this specific " idiochromosome " is large in one half
of the spermatozoa of a male and small in the other half of the sperma-
tozoa. While McClung assumed that the accessory chromosome is
a determinant for the male sex, Wilson shows that it is more probable
that it gives rise to the female offspring.
If we sum up all these data concerning determination of sex, we
therefore come to the conclusion that sex is, in all probability, already
predetermined in the sex cells. In some forms, e.g. Aphides and other
parthenogenetic forms, sex can unquestionably be determined by the
eggs alone, and consequently we must assume here the existence of
two kinds of eggs. In other organisms, like the Hemiptera and Or-
thoptera, we have two kinds of spermatozoa and apparently one kind
of eggs, and in these cases it is the spermatozoon which determines the
sex. There exists apparently a third type of forms, e.g. bees, ants and
social wasps, in which both eggs and spermatozoa share in the deter-
mination of sex, inasmuch as the eggs alone determine the male, while
the spermatozoon determines the female sex; if both are united, the
influence of the spermatozoon predominates. If this is correct in this
group of animals, only one kind of eggs and only one kind of sperma-
tozoa will be found.J
* McClung, loc. cit.
t E. B. Wilson, Science, N. S. Vol. 22, p. 500, 1905.
j It follows from these data that the female egg, or spermatozoon, predetermines
also a different group of instincts from the male egg. Morphologically as well as in regard
190 DYNAMICS OF LIVING MATTER
A good deal of mysticism arose from the fact that the number of
young males and females is so approximately equal in many forms,
e.g. in the human race. The fact, discovered by McClung, that through
the process of chromosome division two kinds of sex 'cells must be
formed in equal numbers in the male of Hemiptera and Orthoptera
removes this source of mysticism.
The fact that all attempts to influence the sex of a developing embryo
have thus far failed, harmonizes with the data given above. Born and
others maintained that it was possible to influence the sex of tadpoles
or frogs, or of the larvae of flies, by the food on which the larvae were
fed. These statements have proved to be untenable.
Maupas and Nussbaum have tried to determine sex, not by any
influence upon the developing embryo directly, but upon its offspring.
They experimented on a Rotifer, Hydatina senta. Nussbaum states
that the mode of nutrition of the female embryo after it leaves the egg
determines whether it will later give rise to large female eggs, or to
small eggs for both sexes. Maupas had stated that the temperature
determines the sex; but Nussbaum disagrees with him, believing that
temperature has no direct effect upon the determination of sex.*
The two sexes differ also in regard to the so-called secondary sex-
ual characters, e.g. the shape of the antennae in male and female
butterflies, etc. The question now arises, Are these secondary char-
acters already predetermined in the egg, or are they secondarily
determined by the maturing or mature sexual glands? If the former
were the case, the castration of the larvae before sexual maturity is
reached should not prevent the development of the secondary sexual
characteristics. Oudemans extirpated the sexual glands in caterpillars
of Ocneria dispar, yet the butterfly showed all the secondary sexual
characters. Professor Kellogg told me that he found that the castra-
tion of the young caterpillars of the silkworms has no effect upon the
formation of the secondary sexual characters. These observations
also agree with the idea that the secondary sexual characters are pre-
determined in the egg, and some of them possibly at as early a stage
as the primary sexual characters.
The idea that the sexual glands determine, e.g. by internal secretion,
to instincts, man and woman represent different species, and inasmuch as for a normal
and happy life the instincts must act as a guide, it would seem erroneous to attempt to
make life for both sexes absolutely identical. It would be equally preposterous, however,
to insist that, for this reason, man and woman should not have equal rights. The traditional
barriers to the rights of women are based, not on physiological grounds, but on the survival
of the savage's idea, who made woman his slave. The adjustment of the sphere of action
of woman should he left to her own instincts and judgment, and not to the dictation of
lawyers and politicians.
* For further information, see Herbst, For??iative Reize in der thierischen Ontogenese,
Leipzig, 1901.
HEREDITY 191
the formation of all the secondary sexual characters, is also refuted by
the following observations. There are cases of hermaphroditism known
in which the one side of the body contained a testicle, the other an
ovary. In hermaphroditic insects of this kind, it has been observed
that the secondary sexual characters differed also on the two sides, the
side with the ovary having a female, the other side a male antenna.
This would be impossible if a substance produced by the sexual glands,
and circulating in the blood, were the cause of the secondary sexual
characters. If, however, the primary as well as certain secondary
characters are already preformed in the egg, it might be well possible
that an egg was already female on one side and male on the other side.
Crampton grafted the heads of one sex upon the bodies of the other
sex in pupse of butterflies, in trying to find out whether the sexual
glands could influence the secondary sexual characters on the head,
but this was not the case. There are then certain secondary sexual
characters which seem to be determined before the sexual glands reach
the mature stage. Certain secondary sexual characters, of course, such
as develop at the period of sexual maturity, are determined by the
development of the sexual glands and fail to appear when these glands
are removed before the time of sexual maturity.
3. Egg Structure and Heredity
The form of the body as well as the instincts of the animal are trans-
mitted through the sexual cells. We are forced to assume that the egg
or the spermatozoon must possess a structure of a degree of complexity
equal to that of the adult, or that the development occurs in a manner
which renders such an assumption unnecessary. It is hardly necessary
to mention that we must choose the latter alternative.
If we examine the living egg of a sea urchin or a starfish, we find
that its contents are chiefly liquid. If such eggs are exposed to a slight
one-sided pressure, e.g. under the cover glass, the surface film or mem-
brane bursts, and the liquid contents can be seen streaming slowly into
the surrounding sea water. In this liquid minute granules are notice-
able, which may be solid, but the main mass of the egg is liquid. The
nucleus is surrounded by a solid film. It is possible or probable that
the chromosomes are, in a certain phase of cell division, solid, or
possess a high degree of viscosity. This follows from the fact that
the form of each individual chromosome remains constant through
all cell divisions. It is obvious that a mass which is to a large extent
liquid cannot possess a structure of such a degree of complexity as
the adult starfish or sea urchin. Moreover, we can observe directly
1 92 DYNAMICS OF LIVING MATTER
that the solid constituents of the body, e.g. the skeleton, are formed
later on, and that its form can, of course, be only indirectly pre-
determined in the egg.
We are therefore forced to conclude that for the transmission of
the hereditary qualities no complicated or morphological structure is
required in the sexual cells. This harmonizes with the idea already
gathered from the preceding parts of this lecture, that chemical
conditions are the bearers of hereditary qualities in the egg, for the
instincts as well as the form of the body.
Driesch has shown that when a single cell of the two- or four-cell
stage in the development of the egg in the sea urchin is isolated, this
cell not only develops into a pluteus, but the mode of development
is not essentially different from that of the intact egg.* It would be
merely a play on words to speak in such a case of regeneration. The
development in the early stages consists in successive divisions of each
cell and the creeping of each of these cells to the surface, so that finally
the mass of cells thus formed is a sphere with cells at the surface, while
a space in the center remains free from cells and is filled with a liquid.
The cells at the surface of this hollow sphere then form cilia at their
external surface, and in this stage the larva, which now begins to swim
through the motion of the cilia, is called a blastula. The next stage
in the development is the growing in at one spot of the blastula, of a
group of cells, into the hollow space of the sphere; and the cells thus
growing in, form finally an inner lining of the cells of the blastula. This
process is called the gastrulation, inasmuch as this inner lining is the
beginning of the alimentary tract of the larva. At this stage the larva
is called the gastrula. Later on large cells are formed, the mesenchyme
cells, which creep to certain places in the gastrula, giving rise to the
skeleton, probably through the secretion of CaC03, or of a substance
that leads to the formation of CaC03. According to Driesch, the pro-
cess of development of a pluteus from an isolated cell of a two- or four-
cell stage of the sea urchin's egg occurs in practically the same way,
as in the case of the development of an intact egg; except that the
larva developing from a single cell of the two- or four-cell stage is smaller
than the normal larva, having only one half or one fourth the mass
of the latter. There may be also slight differences in the development,
owing, as I believe, to a kind of hysteresis, inasmuch as the side of the
cell which was in contact with the other cells of the egg before the blas-
tomeres were separated, acts possibly a little differently from the other
sides. These experiments of Driesch are of great importance, inas-
* For the extensive literature on this subject, see E. B. Wilson's book, The Cell, New
York, 1900 ; or T. H. Morgan's book on Regeneration, New York, 1900.
HEREDITY
193
much as they show how twins, triplets, and quadruplets can originate
from one egg. The lack of any complicated structure in the unseg-
mented egg is, I believe, evidenced very strikingly in the following
observation. I have mentioned in a former lecture that if the egg of
a sea urchin (Arbacia) is put into diluted sea water (equal parts of
sea Water and distilled water), many eggs
will burst, and part of the protoplasm will
flow out, without necessarily being separated
from the rest of the egg. In this case the
normally spherical egg is transformed into a
double sphere or a dumb-bell-shaped mass
(Figs. 35 and 36). This mass may give
rise to a single embryo, or to "Siamese
twins," and whether the one or the other
occurs depends upon the width of the piece
ab (see Figs. 35 and 36) that connects the two spheres.* If this
piece is very narrow, as in Fig. 36, twin blastulae will originate from
such an egg; if it is wide, as in Fig. 35,
only a single embryo will develop from
it. Why this should be so can be readily
recognized. We have already stated that
the cells have a tendency to creep to the
periphery of the egg, thus leaving an
empty space in the center which becomes
the blastula cavity. When the connecting
piece is very narrow, it will be filled with
cells, and the two segmentation cavities
can and will remain separate, and two blastula? will be formed (Fig.
37). If, however, the piece ab is wide (Fig. 38), an open space will
be left in this connecting piece, by which
the two blastula cavities communicate,
and in this case only one blastula cavity,
and hence only one embryo will be formed.
The distorted dumb-bell-shaped blastula
soon becomes spherical (through the
secretion under pressure of liquid into
the interior), and a normal larva results.
These facts prove that as far as the
formation of the blastula is concerned there is no preformed structure of
any high degree of complication present in the egg ; and this is still more
true for the later embryonic formations, which follow the blastula stage.
* Loeb, Archiv fur Entwickelungsmechanik, Vol. 8, p. 363, 1899.
Nucleus
Membrane
Fig. 36.
Fig. 37.
194 DYNAMICS OF LIVING MATTER
In these deformed eggs the distribution of the nuclear material
during cell division is entirely different from that which normally occurs ;
yet normal embryos result. Driesch has shown the same in a different
way; namely, by submitting the developing eggs to pressure. In
eggs thus flattened, the planes of segmentation differ from those of the
normal egg, yet normal embryos are formed. These observations
exclude the idea that the distribution of the nuclear material through
the egg is of importance for the form of the embryo.
Driesch succeeded in causing fertilized sea urchins' eggs to fuse in
a number of cases. Such a fusion of the masses of two fertilized eggs
into one, resulted in the formation of a sin-
gle giant embryo (pluteus).* Such a result
would be inconceivable did the egg possess
a structure of such a degree of complexity
as the adult animal. Zur Strassen f had
already before Driesch's experiments made
the observation that the eggs of a parasitic
FlG_ 38# worm, Ascaris, occasionally give rise to
giant embryos through the fact that two
eggs fuse and that their combined masses now give rise to but one
organism. If the egg possessed a complicated structure, the fusion
of the masses of two eggs could no more give rise to a single individual
of gigantic dimensions than two individual adult animals could be
transformed into one by fusing their masses. I have also observed
that with the proper chemical treatment the eggs of the starfish and
of Chatopterus can be caused to fuse; that from two or more such
eggs a single giant embryo may result.^
Boveri and Driesch assume the existence of a certain simple struc-
ture in the unfertilized egg of the sea urchin. According to Boveri,
the egg protoplasm consists of three layers occupying different parts
of the egg (see Fig. 6, p. 31). These three masses can still be recog-
nized in the first four cleavage cells, but in the eight-cell stage cells
arise which no longer contain all three layers. It is possible that only
such isolated cells can give rise to a single embryo, as contain all three
layers. This may account for the fact that an isolated blastomere of
the four- cell stage can still develop into a normal embryo, while the
same is no longer true for the isolated cell of the eight-cell stage. §
As far as the possible origin of the differentiation observed by Boveri
is concerned, I have noticed in an Ophiurian that the immature eggs
* Driesch, Archiv fur Entwickelungsmechanik, Vol. 16, p. 41 1, 1900.
t Zur Strassen, Archiv fur Entwickelungsmechanik, Vol. 7, 1898.
\ Loeb, Am. Jour. Physiology, Vol. 4, p. 423, 1901.
§ See Lecture 2.
HEREDITY 1 95
are attached like berries on one side to a tissue which is ramified like
the branches of a tree. That side which is attached to the tissue is
free from pigment, while the other part is pigmented. I consider it
quite possible that the difference in structure observed by Boveri in
the egg of the sea urchin, as stated above, is of a purely physical
character; namely, that it consists in the fact that different phases
are represented in the egg. Two liquids separated by a layer of a
more viscous substance might give rise to a differentiation, as noticed
by Boveri. If two eggs fuse, the complete union of the corresponding
layers in both eggs must be possible, in order to produce single
embryos, as would be the case if the contents of two vessels were
mixed, each of which contained oil and water.
That the organs which originate later in the larva, e.g. the skeleton,
are not preformed in the egg from the beginning is obvious, and re-
quires no further discussion.
The idea that any structure which may exist in the undivided
egg is of the simplest physical kind is also corroborated by the ob-
servations made by Chun, Driesch, Morgan,* and Fischel,f on the .
eggs of Ctenophores. The Ctenophores possess a simple bell-shaped
body, the outside of which contains eight ribs or rows of cilia in sym-
metrical distribution. The above-named authors found that if the
first two cleavage cells of the Ctenophore's egg are isolated, a Cteno-
phore originates from each cell; that such a Ctenophore, however,
possesses only four ribs. Fischel found that if the egg of a Ctenophore
is cut into several pieces, and each piece gives rise to an embryo, the
total number of ribs possessed by these larvae never exceeds eight. The
body of a Ctenophore consists mainly of a jelly, or gel, and, in all prob-
ability, this gel already exists in the egg, and determines its shape
and the symmetry relations of the future embryo, inasmuch as the ribs
arrange themselves symmetrically on its surface. It is obvious that
the degree of preformed structure in this case need not exceed the sym-
metry relations due to simple physical conditions. The difference
between the Ctenophore's egg and the sea urchin's egg deserves some
special mention. An isolated blastomere of the two-cell stage of the
sea urchin's egg gives rise to a whole embryo, while an isolated blas-
tomere of the same stage in a Ctenophore's egg gives rise to but a half
embryo, as far as the ribs are concerned. This difference is probably
due to a difference in the viscosity of the contents of the two eggs, the
fluid contents of the sea urchin's egg assuming a spherical shape again
after isolation ; while the blastomere of the egg of a Ctenophore, being
* Driesch und Morgan, Archiv fur Entwickelungsmechanik, Vol. 2, 1895.
t Fischel, Archiv fur Entwickelungsmechanik, Vol. 6, 1897.
196 DYNAMICS OF LIVING MATTER
more viscous and jelly like, keeps the hemispherical shape, even after
its isolation. If this idea is correct, it ought to be much more difficult
to produce a giant embryo by the fusion of the contents of two eggs,
in Ctenophores than in sea urchins, inasmuch as their fusion would be
more difficult on account of the jelly like consistency of the main mass
of the embryo.
It seems that in the egg of Mollusks, also, the simple symmetry
relations of the body are already preformed. It is well known that
there are shells of snails which turn to the right while others turn in
the opposite direction. The shells of Lymnaus turn to the right, those
of Planorbis to the Jeft. It had been observed that the eggs of right-
wound snails do not segment in a symmetrical, but in a spiral, order.
Crampton and Kofoid discovered independently of each other that
in left-handed snails an asymmetrical spiral segmentation occurs also,
but the direction of the spiral is the reverse of that in the segmentation
of the right-handed snails.* The asymmetry of the body in snails is
therefore already preformed in the egg. The conditions which de-
termine such an asymmetry may be of a very simple character.f
From the facts we have thus far discussed it is obvious that in eggs
whose contents possess a high degree of fluidity not much beyond the
simplest symmetry relations can be preformed. A higher degree of
preformation is only possible where liquid and solid constituents are
contained in different parts of the egg.
E. B. Wilson J has recently found a still more marked differentiation
in the eggs of some Annelids and Mollusks than the cases thus far
discussed. Wilson isolated the first two blastomeres of the egg of
Lanice, an Annelid. These two blastomeres are somewhat different
in size ; from the larger one of the first two blastomeres, the segmented
trunk of the worm originates. Wilson found that "when either cell
of the two-cell stage is destroyed, the remaining cell segments as if it
still formed a part of an entire embryo. The later development of the
two cells differs in an essential respect, and in accordance with what
we should expect from a study of the normal development. The pos-
terior cell develops into a segmented larva with a prototroch, an asym-
metrical pre-trochal or head region, and a nearly typical metameric
seta-bearing trunk region, the active movements of which show that
the muscles are normally developed. The pre-trochal or head region
bears an apical organ, but is more or less asymmetrical, and, in every
case observed, but a single eye was present, whereas the normal larva
* Crampton, New York Academy of Sciences, 1894; Kofoid, Proceedings of the Am.
Academy of Arts and Sciences, Vol. 29, 1894.
f Conklin, Anatomischer Anzeiger, Vol. 23, p. 577, 1903.
\ E. B. Wilson, Science, Vol. 20, p. 748, 1904; and Jour. Exper. Zo'ol., Vol. 1.
HEREDITY 197
has two symmetrically placed eyes. The development of the anterior
cell contrasts sharply with that of the posterior. This embryo like-
wise produces a prototroch and a pre-trochal region, with an apical
organ, but produces no post-trochal region, develops no trunk or setae,
and does not become metameric. Except for the presence of an apical
organ, these anterior embryos are similar in their general features to
the corresponding ones obtained in Dentalium. None of the indi-
viduals observed developed a definite eye, though one of them bore a
somewhat vague pigment spot.
"This result shows that from the beginning of development the mate-
rial for the trunk region is mainly localized in the posterior cell ; and,
furthermore, that this material is essential for the -development of the
metameric structure. The development of this animal is, therefore,
to this extent, at least, a mosaic work from the first cleavage onward
— a result that is exactly parallel to that which I earlier reached in
Dentalium, where I was able to show that the posterior cell contains
the material for the mesoblast, the foot, and the shell; while the ante-
rior cell lacks this material. I did not succeed in determining whether,
as in Dentalium, this early localization in Lanice preexists in the un-
segmented egg. The fact that the larva from the posterior cell develops
but a single eye, suggests the possibility that each of the first two cells
may be already specified for the formation of one eye; but this inter-
pretation remains doubtful from the fact that the larva from the ante-
rior cell did not, in the five or six cases observed, produce any eye."
It should, however, be pointed out that the posterior cell, which
in the whole egg only seems to form the segmented trunk of the
animal, forms a head if isolated, although the latter in the cases
thus far observed was not symmetrical. We do not wish to enter
further into this field of experimental embryology, and we refer the
reader, in addition to the papers mentioned here, to those published by
Chabry, Conklin, Driesch, O. Hertwig, Morgan, Pfliiger, Roux, Schultze,
Whitman, Wilson, and many others. It was our intention in this
connection only to show that the first structures in the egg do not seem
to be beyond the reach of purely physicochemical data. On the other
hand, these data corroborate still further the statement that the early
forms of the embryo are determined by the egg, and in no way depend
upon the spermatozoon. It has occasionally been suggested that it
might be possible to produce an organism from a spermatozoon alone,
if the latter were only transplanted into a nutritive medium. This
could only be true if the culture medium used possessed also the typical
structure of the egg, which is not very likely.
Boveri and others have shown that often very early in the develop-
198 DYNAMICS OF LIVING MATTER
ment, part of the substance of the egg is laid aside as the germ from
which the sexual glands develop. While the rest of the egg is
transformed into the various organs of the body, this part remains
what it is ; namely, embryonic matter. This embryonic matter
begins to grow at a certain stage in the development. Miescher*
has investigated this phenomenon somewhat in the case of the salmon.
The salmon leave the ocean and migrate into rivers to spawn.
When they begin to go into the rivers their testicles and ovaries
possess little weight, while their muscles are powerfully developed.
At this time the testicle is only yoVo to Tiro °f the weight of the
whole animal, while a few months later it is 5 per cent of the body
weight. In the female fish the relative weight of the sexual glands
is still more considerable. According to Miescher, the salmon do not
take up any food while they are in the fresh water. The source of
material from which the sexual glands are built up must therefore be
in the animal. Possibly through an increase in hydrolytic processes
this material gets into the blood and is retained by the sexual glands.
Miescher found that the muscles apparently furnished the material
from which the glands are built up. The male and female animals
behave somewhat differently in regard to the utilization of the
material furnished by the muscles. In the sexual gland of the males
the protein taken up from the blood is partly hydrolyzed, and the prod-
ucts, according to Miescher, — protamin, guanin, sarkin, — collect in the
spermatozoa. In the ovaries this hydrolysis does not occur, and the
protein of the blood is utilized for the building up of the eggs whose
mass is considerably larger than that of the spermatozoa. The hydroly-
sis of the muscles is due, according to Miescher, to lack of oxygen,
caused in his opinion by the diminution in the rapidity of the circula-
tion of the blood through the muscles at the time of the growth of the
sexual glands.
* Miescher, Histochemische und physiologische Arbeiten, Leipzig, 1897.
LECTURE XI
ON THE DYNAMICS OF REGENERATIVE PROCESSES
i. Sachs's Hypothesis of the Formation of Organs
The investigation of the physicochemical conditions for the for-
mation of organs in the egg meets with the difficulty that the germ is
too small for a thorough experimental analysis of the processes which
occur there. It seems to me that it will be easier to use for such an
analysis another series of morphogenetic processes; namely, regen-
eration. In many plants and animals when an organ is cut off, a new
organ is formed which is identical with the lost organ. The only scien-
tific hypothesis of morphogenesis which we thus far possess, — namely,
that of Sachs,* — starts with the processes of regeneration.
Sachs takes it for granted that the variety in the form of organs
is determined by a corresponding variety in their chemical constitution.
As an illustration of the relation between chemical constitution and
the formation of organs, he uses his experiences with the influence of
light upon the origin of blossoms. If plants, e.g. Tropceolum majus,
are put into the dark in spring, their flowering buds which are already
formed are not able to develop. In the dark the assimilating power
of the green plant is inhibited, and Sachs concluded that the specific
substances which are required for the formation of the blossoms cannot
be formed by the leaves in the dark. In the light, however, these sub-
stances are formed in the leaves, and are carried by the sap from the
leaves to the nearest flowering buds. Growth was not restricted in
the dark, as was shown by the formation of large (etiolized) shoots
in the dark by the same plants. From this fact Sachs concluded that
if only the quantity and not the quality of the material circulating in
the sap determined the nature of organs, the Tropaolum should have
formed flowers; for the mass of the shoots formed in the dark was a
multiple of the mass of material required for the production of flowers.
* Sachs, Stoff und Form der Pflanzenorgane. Gesammelte Abhandlungen ilber Pflan-
zenphysiolcgie, Vol. 2, p. 1159, Leipzig, 1892. The reader will find a rather complete survey
of the literature on Regeneration in Morgan's book on this subject (T. H. Morgan, Regen-
eration, New York, 1901).
199
200 DYNAMICS OF LIVING MATTER
If the tip of the stem alone is put into the dark, while the leaves are
exposed to the light, the tip forms blossoms. Therefore Sachs con-
cluded that in the light the leaves form substances which are of specific
importance for the formation of flowers. He found in support of this
view that bulbs of tulips, hyacinths, iris, and crocus, if they are caused
to grow in the dark during the spring, produce normal blossoms. In
these plants the material and the specific substances necessary for the
formation of their flowers were stored up during the preceding year.
Sachs generalized this conclusion : Not the quantity of material alone
but also the quality is decisive for the formation of organs. There
are as many specific substances in a plant as there are different organs.
It is obvious that this idea is in full harmony with the experiments of
Mendel and De Vries on heredity, inasmuch as this theory ultimately
forces us to assume specific substances as the determinants for the
hereditary qualities.
To make Sachs's hypothesis as clear as possible, we will quote the
following passage: "We may imagine the process (of organization)
as being in a way comparable to the successive processes in a chemical
factory, where from the original raw material chemical compounds of
the greatest variety are formed in succession until the final product
is obtained chemically pure, possibly in an extremely small quantity.
Although our analyses seem to indicate apparently always the same
protoplasm, starch, sugar, fat, we must realize that these substances
may themselves differ,* or that traces of other substances may force
them to solidify in different organic forms. To give one example,
it seems that the formation of flowers and seeds depends upon a
storing up of phosphates in these organs, that the plant cannot form
flowers and seeds until there is a comparative excess of phosphates com-
pared with the other ashes in the saps. . . . An excess of phosphates
may force a beet to produce flowers in the first instead of the second
year." Sachs applied the same idea to the problem of regeneration.
If we cut a piece from the branch of a willow tree, it will under the
proper conditions, form roots near the basal and shoots near the apical
end. Sachs raises the question as to how it happens that the cutting
off of a piece causes the formation of organs in places where it would
never occur without this operation or other disturbing conditions. The
question is answered by Sachs in harmony with his above-mentioned
hypothesis. Duhamel had assumed the existence of two currents of
sap in the plant, one ascending, the other descending; the latter carry-
ing root-forming, the former stem-forming, material. Sachs imagines
that "as long as a green plant with an upright stem is nourished and
* E.g. Stereoisomeres.
DYNAMICS OF REGENERATIVE PROCESSES 201
growing, the specific formative substances of the root flow from the
assimilating leaves to the root at the lower end of the stem; while the
shoot-forming substances flow from the leaves upward to the apices
of the twigs. If a piece be cut out from the stem or the root, the cut
surfaces form an obstruction where these substances now gather." In
such a piece the root-forming substances will therefore gather at the
basal end of the twig, and cause here the formation of roots; and the
shoot-forming substances will collect at the apical end where they favor
the formation of shoots. Sachs's hypothesis finds a beautiful confirma-
tion in the phenomena of regeneration in leaves. The leaves are the
factories in which the carbohydrates, and perhaps all the specific sub-
stances in the sense of Sachs, are formed. The dissolved substances
flow from the leaves to the base, and from here to the stem. If pieces
be cut from a leaf, e.g. in a Begonia, shoots as well as roots are formed
at the basal end of the leaf where the substances flow. Goebel has
added a great many beautiful observations on regeneration in plants
which support Sachs's conclusion.
The observations of pathologists on compensatory hypertrophia
support also in my opinion the idea of Sachs.* If, e.g., one kidney is
removed, the other increases in mass. The same seems to hold also
for other glandular organs. Pathologists assume that this is due to
the greater work now done by the remaining gland. If the hypothesis
of Sachs is applicable here, it is possible that certain substances which
caused the growth of these glands circulate only in limited quantities
in the blood. If a gland be removed on one side of the body, these sub-
stances will all flow through the remaining organ which will, therefore,
begin to grow.
2. Heteromorphosis and Regeneration in Tubularia
The only way which seems to lead directly to any information concern-
ing the dynamics of regeneration lies in our finding means to substitute
at desire one organ for another. The results thus obtained no longer
rest upon surmises, but allow us to determine the variables of which
the process of regeneration is a function. Sixteen years ago I under-
took to bring about such substitutions of one organ for another at
desire. I succeeded in a number of hydroids and an ascidian, and
called the process heteromorphosis f to discriminate between this
phenomenon and the substitution of an organ by an identical one
* Loeb, Untersuchungen znr physiologischen Morphologie dtr Titre, Wiirzburg, 1890
and 1 89 1. (Translated in Studies in General Physiology, Chicago. 1905.)
f Loeb, loc. cit.
202 DYNAMICS OF LIVING MATTER
regeneration). Since then heteromorphoses have been obtained in a
number of animals.
Tubularia mesembryanthemum of the Mediterranean and Tubu-
laria crocea of the Pacific Ocean are hydroids which consist of an un-
divided stem (ss, Fig. 39) from 2 to 6 cm. long, which
has a polyp (p, Fig. 39) at the oral, a stolon or foot w at
the aboral end. If a piece ab (Fig. 40) is cut from the
stem of a Tubularian, according to the observations of
Allman, a polyp forms at the oral end a, a stolon at the
aboral end b. Allman therefore called this animal "polar-
ized," thereby signifying that each element of the stem of
the animal possesses a different oral and aboral side. I
undertook to bring about a heteromorphosis in this animal,
and succeeded in finding a method by which without fail at
the aboral cut end b of a piece of the stem a polyp can be
produced. This method consisted in putting the piece ab
, , 1(. with its oral end a into the sand, while the aboral end b
was surrounded by water on all sides. In this case a polyp
instead of a stolon was invariably formed at the aboral end b. The
oral end which is in the sand does not regenerate, presumably on
account of the lack of oxygen. When both ends of a piece
ab cut from the stem of a Tubularian are surrounded by sea
water, the oral end a invariably forms a polyp. The aboral
end b may form a stolon or a polyp. In Tubularia crocea
I observed that under such conditions the aboral ends form
polyps in about 90 per cent of the cases, and stolons in
about 10 per cent! In this case 90 per cent of animals
were obtained with a head at either end (see Fig. 41).
There was, however, a marked difference in the velocity
of regeneration of the two polyps. The polyp at the oral
end forms without exception more quickly than the polyp
at the aboral end. The difference in time may vary from
two days to two weeks; the difference apparently being less
at a high than at a low temperature. Even if the piece of
the stem forms a head at either end an intimation of the old polarity
still exists, inasmuch as the oral pole is formed earlier than the aboral
pole.*
In the following year I was able to show that the formation of the
polyp at the aboral end could be accelerated by suppressing the forma-
tion of the polyp at the oral end. The mode of procedure of demon-
strating this fact was as follows: Pieces ab (Fig. 40) were cut from a
* Loeb, loc. cit., 1890.
a,
DYNAMICS OF REGENERATIVE PROCESSES 203
number of Tubularian stems ; one half of these pieces were put ver-
tically, but reversed, i.e. with the oral end a in the sand, in order to
suppress the formation of polyps at this end. The
other half of the pieces were also put vertically and
reversed into the same aquarium, but in such a way ^MM^
that both cut ends a and b were surrounded by sea
water. These latter pieces formed polyps at the oral
end a after three or four days, while it took nine days
for them to form polyps at the other end. The
stems, however, whose oral ends were put into
the sand, where consequently the formation
of polyps at the oral end was suppressed,
formed polyps at the aboral end within
three or four days.
Hence, the suppres-
sion of the forma-
tion of the polyp :^^^r^^^^^^^u^ q,
at the oral end FlG
accelerated con-
siderably* the formation of the polyp at the aboral end.
The next question was, How can the suppression of the polyp at the
oral end accelerate the formation of "the polyp at the aboral end ? The
following experiments were intended to answer this question.
Pieces ab (see Fig. 42) were cut from a number of stems,
and each of these pieces was cut in two between c and d. If
all four cut ends were surrounded by sea water, polyps were
first formed at the oral end of each half; namely, at a and
d, where the polyp formation occurred simultaneously. Con-
siderably later the polyps were formed at the aboral ends
c and b, and here also the polyp formation occurred simul-
taneously. It therefore appears as if the polarity in this
case were due to a condition of the nature of a current (e.g.
of liquid), by which certain substances were carried through
the stem in the direction from the aboral to the oral end.
FlG The deposition of certain substances by the current at the
anterior end retards the formation of the polyp at the opposite
end. The idea that a current is the decisive variable in this case could
be tested in another way ; namely, by tying a ligature around the stem
in the middle. If this is done, the polarity is done away with and a
polyp is formed simultaneously at both ends.f The same experiment
* Loeb, loc. cit., II, 1891.
f Loeb, Pfliiger's Archiv, Vol. 102, p. 152, 1904.
204
DYNAMICS OF LIVING MATTER
was made from a different point of view independently by Godlewski.*
Through the ligature the current which carries away substances from the
aboral end is inhibited, and hence the cause for the polarity is removed.
When I first made these experiments the hypothesis of Sachs seemed
to suggest that in the excised piece of a stem not enough specific polyp-
forming material was present to allow the simultaneous forming of two
polyps, but the experiments already mentioned exclude this idea. It is
further excluded by the observations made by Miss Bickford, who
found that even if a stem be cut into a number of small pieces, each
oral end of such a piece forms a polyp. Hence it is not a question of
lack of material but only a lack of free cut ends, which block the flow
of sap, if only one polyp is formed in a piece cut from the stem of a
Tubularian. It is therefore apparently the process of streaming itself
which may take something away from the aboral end, which is responsi-
ble for the fact that a stolon is formed here, or if a polyp be formed that
its formation is delayed.
As far as the method of regeneration is concerned, Miss Bickford
has found that it does not consist in the growth of a new polyp from
the old material, but in a direct transformation of the
material of the stem into a new polyp. Miss Bickford
observed this directly under the microscope in small
pieces from the stem of a Tubularian, which were not
even of the size of a normal polyp. In such cases the
whole mass of the piece was transformed into a polyp. f
In the case of the smallest pieces the result was still
more striking. At each free end of the small piece of
the stem tentacles and a proboscis were formed (Figs. 43
and 44), but inasmuch as there was no material left for
the formation of a stem in addition to two polyps, or
not even for two entire polyps, a kind of Janus head
was formed, two faces or probosces of a polyp looking
in opposite directions. No new outgrowth occurred,
but the old tissues arranged themselves into a new
shape, forming a polyp, while before they had formed
part of the stem. The most remarkable fact was the
transformation of certain cells of the entoderm into
secretory cells of the stomach.
It is not yet possible to tell exhaustively which forces
have to do with this transformation. The stem is
surrounded by a chitinous layer. I have never observed the formation
* Godlewski, Archiv fur Entwickelungsmechanik, Vol. 1 8, p. Ill, 1904.
f Elizabeth E. Bickford, Jour, of Morphology, Vol. 9, p. 417, 1894.
Fig. 43. — After
Miss Bickford.
Beginning of the
formation of
two polyps in-
side a piece
from astern of
Tubularia.
DYNAMICS OF REGENERATIVE PROCESSES
205
of a polyp inside of the intact stem, but only where the cells inside
the chitinous layer come in contact with the sea water. The mere
interruption of the continuity of a stem does not
seem to suffice, as I have never seen the formation
of a polyp at the point where the stem was ligatured.
It is possible that the lack of oxygen is responsible
for the fact that no polyp can be formed except at
a free end of a stem, since the chitinous surface of
the stem is very little permeable for oxygen.
A second condition is the closing of the body
cavity after the cut is made and the establishment
of a circulation. The body of the Tubularian
hydroid is a long, hollow cylinder, and the hollow
space in the center of a Tubularian is divided by
a septum into two chambers which communicate
at the ends (a and b, Fig. 45). In this space a
circulation of the liquid is maintained by the
ciliary motion of the endothelial cells in such a
way as to make the flow of liquid ascending on
one side and descending on the opposite side. This
stream carries red and yellowish pigment granules
which are apparently formed by the cells of the en-
dothelium. The analogy with similar cases suggests the possibility that
these pigments are respiratory pigments, serving a purpose similar to,
e.g., the red blood corpuscles in our body. If we now cut
out a piece from the stem of the hydroid, the opening at
either end closes in an hour (more or less according to the
temperature) by the cells of the cut end spreading out over
the opening concentrically.* According to my observations,
no piece of a hydroid can regenerate unless this circula-
tion is established. This may be due to the fact that the
circulation serves as a means of supplying oxygen, and a
liberal supply of oxygen seems to be an absolute prereq-
uisite for all phenomena of regeneration and growth. Any
piece of a Tubularian, however, which can establish a cir-
culation can form a polyp. Thus, when a stem is split
lengthwise, the cellular masses may become disconnected
into several pieces. Each such piece may form a polyp at
both ends.
When we ligature a stem in the middle, the circulation will be inter-
rupted, inasmuch as at a place where the ligature is made the septum
* E. Bickford, loc. cit.
Fig. 44. — After Miss
Bickford.
The same specimen a
little later, after the
formation of the
polyps was com-
pleted. The chitinous
tube was removed.
Kj
M
b
Fig. 45.
206 DYNAMICS OF LIVING MATTER
is not perforated. Very soon, ' however, after the ligaturing, a
perforation at the septum on either side of the ligature occurs, and
the circulation is again established. One might think that the current
just described was responsible for the phenomena of polarity in Tubu-
larians, inasmuch as this current carried away certain material from
the aboral pole. The direct observation supports this idea to some
extent. As I pointed out fifteen years ago, the place where a new polyp
will be formed is always recognizable some time before the actual regen-
eration occurs, by the collecting of the red or yellow pigment granules
in greater density at that spot. It agrees with this statement that if a
piece be cut out from the stem of a Tubularian and suspended in sea
water, the red pigment always collects first in great masses at the oral
end, where the polyp is formed first, and only later at the other end. In
my earlier writings on heteromorphosis I pointed out that this seems to
be in harmony with Sachs's idea, inasmuch as it indicates a migration
and collection of definite substances at the end of a regenerating piece as
the cause of the formation of a new organ. Morgan and Miss Stevens
raised the objection that after the formation of the polyp the rem-
nants of these red granules are thrown out by the polyp. This seems
to me in no way to speak against the possibility that the red granules
contribute some substances necessary to the formation of the polyp. As
is well known, the red blood corpuscles perish regularly in the body,
and their products of decomposition form constituents of the bile. Yet
nobody would think of using this fact as an argument against the
importance of the red blood corpuscles or the bile. I am inclined to be-
lieve that Morgan and Miss Stevens underestimate the fact which Sachs
tried to emphasize, that chemical processes underlie the phenomena of
regeneration.
But I am far from believing that the circulation current is the only
factor in the transport of substances through the Tubularian. It is
possible that in Tubularia we are dealing also with a current of sap
through specific tissue, as is found in plants. Setchell has made it
probable that in Laminaria regeneration always starts from that tissue
which conducts the nutritive material. It may be that there exists a flow
of material from cell to cell in the entoderm or ectoderm of the Tubu-
laria or both, and that this flow occurs naturally from the aboral to the
oral end, but that it is reversed in the aboral piece of the stem when
a ligature is made in the stem. Even if the fact that the pigment gran-
ules are carried away from the rest of the stem and are gathered
at the oral end be responsible for the polarity, it remains to be ex-
plained what keeps the granules rather at that than at the opposite end.
These details still have to be worked out, but I believe that we may
DYNAMICS OF REGENERATIVE PROCESSES 207
consider it as established experimentally that the conditions which de-
termine the morphological polarity are due to something of the nature
of a current inside of the Tubularian. The mysterious morphological
polarity is thus reduced to a polarity which can be expressed in physical
or physicochemical terms. We see that this result differs in one point
from Sachs's hypothesis. The latter includes the effect of specific sub-
stances, while this condition does not appear in the results of our experi-
ments. It is, however, hardly necessary to state that our experiments by
no means exclude this possibility. I have discussed the case of regen-
eration in Tubularians at some length, not only because it is well known
to me through my own experiments, but also because on account of
its simplicity, it lends itself better to a reduction of dynamically
unintelligible morphological data to the more rationally expressible physi-
cal or physicochemical conditions.
Osterhout and I tried to test the effects of a ligature on plants, espe-
cially on willow twigs. As we have already stated, a piece cut out from
a willow twig forms roots first at the basal and shoots at the apical end.
The process of regeneration in this case differs in several essential fea-
tures from that in Tubularians. The formation of the new organs
occurs in the willow twig not at the cut end but at the anlage of the
roots and shoots, both of which exist here normally. All that the opera-
tion does in this case is to cause the anlage of roots which would never
have developed now to grow out into roots. The reader should realize
that the anlage of the roots which begin to grow in consequence of the
cutting off of the twig is not injured by the operation and is often far
removed from the wound. The idea that this anlage grows out be-
cause the sap which would otherwise flow downwards is now blocked
by the cut, and becomes available for the anlage of the roots, looks very
plausible in the light of the actual facts. As part of the sap flow can
be suppressed by a tight ligature around the rind of a stem, Osterhout
and I tried the experiment of ligaturing a number of willow twigs in
the middle. The result was that a ligature caused the root anlage
above it and the shoots below it to develop, which without the ligature
would not have developed. In the case of the willow, we are also deal-
ing with a flow of material through conductive tissue, i.e. tissue through
which nutritive material is conducted.
3. Regeneration in an Actinian [Cerianthus membranaceus)
The phenomena of regeneration in Cerianthus can be easily under-
stood from the experiments on Tubularians, if we imagine the body
wall of Cerianthus to consist of a series of longitudinal elements which
208
DYNAMICS OF LIVING MATTER
Fig. 46.
run parallel with the axis of symmetry of the animal from the tentacles
to the foot. The number of these elements may be supposed to corre-
spond to the number of the outer row of tentacles of the normal animal.
Each such element behaves like a Tubu-
larian, with this difference, however, that
the elements in Cerianthus are more strongly
polarized than Tubularia. No heteromor-
phosis has thus far been produced in these
elements in Cerianthus, and each one is
able to form a tentacle at its oral pole
only. This fact can be nicely illustrated
in the following way : if a square or oblong
piece {abed, Fig. 46) be cut from the body
wall of a Cerianthus in such a way that one
side, ac, of the oblong is parallel to the
longitudinal axis of the animal, tentacles
will grow on one of the four sides only;
namely, on the side ab* The three other
free edges are not able to produce tentacles. If an incision be made
in the body wall of a Cerianthus, tentacles will grow on the lower
edge of the incision (Fig. 47).
I have recently tried whether or not by tying a ligature round the
middle of a piece of an Actinian this polarity could
not be suppressed. But the experiments did not
succeed, inasmuch as the cells compressed by the
ligature died, and through bacterial action were
liquefied so that the pieces in front and behind the
ligature fell apart. It is therefore impossible to
decide whether or not a condition of the nature of a
current or a flow of substances in a certain direction
through these elements is responsible for this polarity,
though I consider this probable. I found, however,
that one condition is necessary for the growth and
regeneration of tentacles which also plays a role in
the corresponding phenomena in plants; namely,
turgidity. The tentacles of Cerianthus are hollow
cylinders closed at the tip, and by liquid being
pressed into them they can be stretched and appear
turgid. If, however, an incision is made in the body,
the tentacles above the incision can no longer be stretched out (Fig.
47). I have found that the turgid condition of the tentacles is neces-
* Loeb, Untcrsuchungen zur physiologisch.cn Morphologic dcr Thierc.
Fig. 47.
DYNAMICS OF REGENERATIVE PROCESSES
209
sary for their growth. In one experiment the oral disk of a Cerianthus
was cut off ; very soon new tentacles began to grow at the top, and
after having reached a certain size, an incision was made in the animal
at d, Fig. 47. The tentacles above the incision between b and c, Fig.
47, collapsed in consequence and ceased to grow, while growth of the
others between a and b continued. On the lower edge of the incision
new tentacles began to grow.
Child* has elucidated to some extent these phenomena of turgidity.
Every tentacle is a hollow cylinder, and this cylinder continues down-
ward where it communicates with the body cavity. When liquid is
pressed into the tube from the body cavity, the tentacles are stretched ;
but if the liquid leaves the tube, the tentacles relax also. If an incision
is made below a tentacle into the wall of the body of a Cerianthus, no
more liquid can be pressed into that tentacle, and it relaxes. Child con-
firmed my observation, that regeneration of the tentacles in Cerianthus is
no longer possible when they relax. He added a number of pretty
demonstrations of the necessity of the
turgidity of the tentacles for regeneration.
He found, for instance, that if an incision
is made into the foot of a Cerianthus and
the edges of the wound are prevented
from healing together the tentacles lose
their turgidity and are no longer able
to grow. He found, also, that the ten-
tacles degenerate under such conditions.
It is unknown at present how the
turgidity can influence growth in the
tentacles of an Actinian.
The observations on Cerianthus are
comparable with those on Tubularia if
we realize that the body wall in Cerianthus
consists of a series of hollow cylinders or
spaces each of which ends in a tentacle.
The idea of an animal body consisting
of a series of comparatively independent
longitudinal elements recommends itself
also for the understanding of a phenom-
enon of regeneration in Ascidians. The
Ascidian, Ciona intestinalis, has eyes
(ocelli) at the oral as well as at the aboral opening of the body (Fig.
48). We may imagine that each ocellus is the end of one of the
* Child, Biological Bulletin, 1903-1904.
Fig. 48.
An incision was made at c and new
ocelli develop at both ends of the
cut.
2IO
DYNAMICS OF LIVING MATTER
longitudinal elements to which reference was just made. If a lateral
incision be made in the body at c, not too far from the openings, ocelli
will be formed at each free end of these elements. Here the longi-
tudinal elements show heteromorphosis, inasmuch as they are capable
of forming ocelli at both ends.
I am inclined to believe that in each of these cases the individual
longitudinal element represents a conductor for nutritive material or
specific morphogenic substances in the sense of Sachs. It must remain
undecided for the present whether this flow occurs through the hollow
space or through the tissue or certain cells of the tissue.
4. Regeneration and Heteromorphosis in Fresh-water
Planarians
It had been known for a long time that if the head and the tail be
cut off from a fresh-water Planarian, at the front end a new normal
head, at the back end a new tail, will be
regenerated (Fig. 49). Morgan* made the
interesting observation that if a piece acdf
be cut obliquely (Fig. 50) instead of at right
angles to the
longitudinal
axis from a
Fig. 49. — After Morgan. Planarian, a
tiny head is
formed at the foremost corner of the piece
a and a tiny tail at the hindmost corner /,
Fig. 51. Why is it that in the oblique
piece the head is formed in the corner
and not all along the cut surface as is the
case when the cut is made at right angles
to the longitudinal axis? I am inclined
to believe that the right answer to this
question has been given by Bardeen.f
Bardeen has pointed out the apparent role
that the circulatory (or so-called digestive)
canals in Planarians play in the locali-
zation of the phenomena of regeneration, inasmuch as the new head
always forms symmetrically at the opening of the circulatory vessel
* Morgan, Regeneration, New York, 1901.
t Bardeen, Am. Jour. Physiology, Vol. 5, p. I, 1901 ; and Archiv fiir Entwickelungs-
meckanik, Vol. 16, p. 1, 1903.
Fig. 50. — After Morgan.
DYNAMICS OF REGENERATIVE PROCESSES
211
or branch which is situated as much as possible at the foremost end
of the regenerating piece of worm. He assumes that through the
muscular action the liquids of the body are forced to stream toward
this end, and that this fact has some connection with the form-
ation of a new head. There can be no doubt that the facts here
mentioned agree with Bardeen's suggestion. The oblique pieces in
Morgan's experiments, which have at first the heads and tails outside
the line of symmetry of the middle piece, gradually assume afterward
a normal position (Figs. 51-54). I am inclined to believe as Child
Figs. 51-54. — After Morgan.
Successive stages in the regeneration of the oblique piece adcf of Fig. 50.
does that this is due to purely mechanical conditions. The head of
such an oblique piece is asymmetrical, the one side ab being less stretched
than the other side be. The higher tension of the piece be will have the
effect of bringing b nearer c. The reverse is true for the tail def, and
the effect will here be that e will be pulled nearer d. In this way purely
mechanical conditions are responsible for the fact that the soft tissues
of the animal are gradually restored to their true orientation.*
It was of interest to find out whether heteromorphosis could be pro-
duced in Planarians. At my request Dr. Van Duyne undertook experi-
ments in this direction and succeeded in a few cases. f Figure 55 shows
one of these instances. On the right side of the animal the posterior
part had been cut off. A new head which was directed backward was
regenerated in place of the amputated part. Morgan was more suc-
cessful later on. He obtained a larger number of heteromorphoses by
cutting short pieces out of a Planarian than by cutting out long pieces. %
* It is in mv opinion not only unnecessary but directly confusing to introduce for the
explanation of these phenomena of restitution such mystical forces or conceptions as Noll's
" Morphassthesia," and similar things.
t Van Duyne, Pjluger's Archiv, Vol. 64, p. 56Q, i8q6.
% Morgan, Archiv fur Entiuickelungsmeckanik, Vol. 17, p. 683, 1904.
212
DYNAMICS OF LIVING MATTER
He mentions that in the short pieces less "polarity" exists than in the
long pieces; but as the conception of heteromorphosis is the opposite
of polarity, Morgan's statement is only a different way of expressing
the same fact. I remember that when Miss
Bickford made her experiments on regeneration
in Tubularians in my laboratory, I was struck
with the fact that in the very small pieces cut
out of a stem the polyps at the oral and the
aboral end developed practically simultaneously.
Here, too, polarity was less pronounced in small
pieces than in large pieces. I believe the reason
for this lies in the role which processes of the
character of a current or a flow of material play
in these phenomena. The red pigment, and
possibly other substances which are of importance
for regeneration, gather not in one point but in
an area of the length of several millimeters,
where a polyp is to be formed. If the regener-
ating piece is in itself only a few millimeters
long, the pigment must remain scattered equally
over the small piece, and hence the polarity
must disappear. Something similar may occur
in the case of a Planarian. If the piece is
very small, the head-forming material will remain equally distributed
through the whole length of the piece, and hence the chance for the
simultaneous formation of the head at either end is greater than in a
large piece.
It is a general experience that in order to get a duplication of organs,
the regenerating animal must be split into two pieces. Thus, in order
to obtain two larvae from one egg, the egg must be cut into two, or the
heap of cells must be separated into two parts. One might believe that
in order to get two heads in front of a Planarian, the front end would
have to be separated into two by a longitudinal incision. Two heads,
however, often develop in front of a Planarian whose head has been
cut off without such an incision. The explanation is obvious on the
basis of Sachs's hypothesis. If the gathering of certain substances at
the front end is the cause of the formation of a head, and if we assume
with Bardeen that these substances are carried to the cut by the circu-
latory system, it is comprehensible that in two different spots at the
front end substances necessary for the formation of the head may
gather.
Fig. 55. — After Van
Duyne.
DYNAMICS OF REGENERATIVE PROCESSES 213
5. On the Influence of the Central Nervous System upon
Regeneration and on Phenomena of Correlation in Regen-
eration
It is rather remarkable that the central nervous system plays an
important role in phenomena of regeneration. In 1889 I noticed that in
Thysanozoon Brochii, a marine Planarian, the isolated head containing
the ganglia is capable of rapid regeneration while the body without the
ganglia shows less, or a slower regeneration.* The taking up of food
is not responsible for this difference, since the head cannot take up food.
That the taking up of food is not essential for regeneration follows also
from the observations on the regeneration of pieces cut from the walls
of Cerianthus. We must not overlook the fact that the reversible chemi-
cal processes in the cells of an animal are liable to provide material for
regeneration in the same way as the taking up of food.
A number of observers — T. H. Morgan, Child, Lillie, and Lillian
Morgan — have since found that the oesophageal ganglia exercise a con-
siderable influence upon regeneration in marine Planarians.f
It is therefore obvious that there exists a typical difference be-
tween fresh-water and marine Planarians, since in the fresh-water
Planarians the presence of the oesophageal ganglia is not required for
complete and rapid regeneration.
This difference in the influence of the oesophageal ganglia in marine
and fresh-water Planarians upon regeneration finds a probable expla-
nation in a fact to which
Bardeen has called attention;
namely, that the longitudinal
nerves which go through the
whole body of the Planarians
are very rich in ganglia in the
fresh-water Planarians and
very poor in ganglia in Thysa-
nozoon.
Herbst t has discovered the
most beautiful case of hetero-
morphosis thus far known; fig. 56. -After herbst.
namely, that in Crustaceans in
the place of an eye which has been cut off, an entirely different organ,
an antenna, can be formed (Fig. 56). Herbst proved, moreover, that
* Loeb, P/luger's Archiv, Vol. 56, p. 247, 1894.
f Lillian Morgan, Biological Bulletin, Vol. 8, 1905.
j Herbst, Archiv fur Entwickelungsmechanik, Vol. 9, p. 215, 1900; and Vol. 13, p. 436,
1901.
214
DYNAMICS OF LIVING MATTER
the experimenter has it entirely in his power to determine whether the
Crustacean shall regenerate an eye in the place of the eye which has
been cut off, or an antenna. It depends upon the fact whether or not
in the operation the optic ganglion is removed with the eye. If the
optic ganglion is removed with the eye, an antenna is regenerated in
the place of the eye. If the optic ganglion is left intact, a new eye is
formed. These experiments were carried on successfully in Palaemon,
Palaemonetes, Sicyonia, Palinurus, and other Crustaceans. Herbst says
that the optic ganglion exercises a "formative stimulus" upon the
hypodermic cells of the wound. It is certain that an explanation of
the role of the ganglion can only be given in physical or chemical
terms; that as long as this is not possible we possess no explanation.
Morgan has made a somewhat similar observation on earthworms,
in which he found that a new head is only possible at the anterior cut
end of the nerve cord.* The following
case may be mentioned by way of illus-
tration. A few of the anterior segments of
an earthworm were cut off, H, Fig. 57, and
from the remaining body a piece ab was
cut from the anterior part of the nerve cord
(see Fig. 57), while all the other tissues
remained unaltered. The anterior cut end
a of the worm healed, and no new head
formed at this place. Instead, a new head
was formed in some such cases at b, at the
anterior cut end of the nervous system. If
the head alone is cut off in an earthworm
without the excision of the anterior piece
of the nerve cord, a new head is formed at
the anterior end of the body. In another
series of experiments Morgan cut off the
head H of an earthworm and in addition
(Fig. 58) excised a piece be from the nerve
cord, so that now two anterior cut ends, a
and c, Fig. 58, of the nerve cord existed.
In a few of these cases two new heads were
AfterTmorgan. After! morgan, formed, one at each of the anterior ends of
the nerve cord, at a and at c.
Another example of the dependence of the regeneration of one organ
upon the presence of another is found in the formation of the lens of
the eye. As is well known, the formation of the lens in the eye is pre-
* Morgan, Regeneration, p. 52, New York, 1901.
Fig. 57.
Fig. 58.
DYNAMICS OF REGENERATIVE PROCESSES 215
ceded by the formation of the optic vesicles, and where the latter
touch the ectoderm a proliferation of cells begins, from which later the
lens is formed. Spemann* has shown in the salamander that if the
optic vesicle does not reach the ectoderm, no lens is formed. The same
author showed, moreover, that if in the embryo the optic vesicle is
destroyed, no lens is formed, but that if afterward the optic vesicle is
regenerated, a lens is formed as soon at this vesicle touches the ecto-
derm. Lewis confirmed and enlarged Spemann's observations.f
He showed that the ectoderm in frogs can form a lens at any place
in the body if the optic vesicle is transplanted and allowed to come in
contact with the ectoderm. He suggests that definite chemical reac-
tions may occur between certain substances of the optic vesicles and the
cells of the ectoderm; that these substances determine the formation
and the peculiar character of the cells of the lens. This suggestion is
in harmony with the ideas of Sachs, and I am inclined to believe that
it will lead to further discoveries. Lewis's experiments also throw light
upon an earlier observation made on salamanders. It was found that
if a lens is removed in a salamander it can be regenerated from the
iris. Inasmuch as the edge of the iris is naturally in contact with the
retina (optic vesicle), this is about what should be expected from Lewis's
experiments.
It is well known that the skeletal muscles degenerate if separated
from the centers of their motor nerves. Goltz and Ewald have cut
long pieces from the spinal cord in dogs, and observed that all the mus-
cles belonging to the excised segments of the spinal cord degenerated, as
was to be expected. This may be due to some chemical change in the
muscles, owing to their inactivity after the motor nerves are cut or sepa-
rated from their ganglia.
We have already discussed one case of an apparent action at a dis-
tance in Tubularians, where the suppression of the process of regener-
ation at the oral pole accelerated the formation of a polyp at the aboral
pole. Przibram found a case of distance action which is not so easy
to explain. J In a Crustacean, Alpheus, the right and left chelae are
not equal in size and form. The same type of chela is not always on
the same side, but in about one half of the cases the one type is on
the right side, in the other half, the other type. Przibram found that
if the larger of these chelae is removed in such a Crustacean, the remain-
ing chela assumes after the next moulting the shape of the removed
chela, and the regenerating chela assumes the shape which the remain-
* Spemann, Sitzungsber. der phvsik. med. Gesellschaft in Wilrzburg, 1901.
t Lewis, Am. Jour. Anatomy, Vol. 3, 1904.
% H. Przibram, Archiv fur Entwickelungsmechanik, Vol. II, p. 329, 1901.
2l6 DYNAMICS OF LIVING MATTER
ing smaller chela originally had. Thus the animal is normal again, but
the relative position of the two chelae is now reversed. If later on in
such an animal the larger chela is cut, the original order can be obtained
again.
E. B. Wilson has repeated the experiments of Przibram, and made
the important discovery that the growth of the smaller chela after the
removal of the larger one does not occur if the nerve of the former is
previously cut.* The number of the successful operations was small,
but the results were significant. This brings Przibram's experiments
into a line with Herbst's and Morgan's.
It seems to follow from these facts that the nerves have a function
which is different from that of a mere conductor of stimuli; namely,
that of causing the growth or development of certain organs. It has been
argued that these two functions are not different, inasmuch as in both
cases the nerve acts only as a conductor of stimuli and that these stimuli
determine the phenomena of regeneration mentioned here. Child ex-
presses such a view, and Herbst's idea of " formative stimuli " is only a
somewhat less definite expression of the same view. It seems to me that
there exists a still different possibility ; namely, that the nerve may also
act as conductor for certain substances which go from the periphery
to the ganglion cells or in the reverse direction and are carried through
the axis cylinder. Especially the observations of Lewis and possibly
those of Herbst and Przibram suggest such a possibility. But before
we admit the possibility that the axis cylinder can act as a conductor
for the passage of definite substances, we must look for facts which war-
rant such an assumption. Such facts are given by the beautiful dis-
covery of Hans Meyer f that the tetanus toxin is carried from the wound
to the central nervous system through the axis cylinder of the nerves,
and neither through the blood vessels nor the lymphatics nor the sheaths
of the nerves. It is hardly necessary to emphasize the fact that through
this discovery an entirely new light is thrown upon the role which the
nerves or ganglion cells may play in the phenomena of regeneration.
The possibility now arises that the axis cylinder may act as a conducting
path for certain substances which in some animals may be necessary
for the starting of a process of regeneration or which may modify the
nature of the organ which is to be regenerated.
A few words may finally be said about the well-known effects of
certain organs like the hypophysis and the thyroid gland on phenomena
of growth. Certain parts of the body — namely, the lower jaw, the
* E. B. Wilson, Biological Bulletin, Vol. 4, p. 197.
f Hans Meyer, Festschrift fur Jaffc, 1901. Meyer und Ransom, Archiv fur Experim.
Pathol, und Pharmacol., Vol. 49, p. 369, 1903.
DYNAMICS OF REGENERATIVE PROCESSES 217
fore arm, the hand, and the leg from the knee down — may suddenly be-
gin to grow even if the body had already reached its final size. This
phenomenon, known as acromegaly, is comparable to the process of re-
generation, inasmuch as the problem in this case is also what causes
this sudden growth which normally does not occur. It has been ob-
served that this disease is often connected with a degeneration of the
hypophysis, a small organ of enigmatic function. An attempt has been
made (Von Cyon) to cure this disease by feeding the patient on normal
hypophyses. This idea is based on experiences made in regard to the
thyroid gland. Complete extirpation or degeneration of the thyroid gland
in growing persons causes a standstill of growth and sexual and mental
development. It has been found that if such patients be fed on thyroid
glands, the growth and development can be again started. This seems
to speak in favor of the idea that the action of specific substances may
cause the post-adult growth of arms and legs in the case of acromegaly.
It may, however, be a case of growth due to nervous influences com-
parable to the experiences of Przibram in Alpheus.
6. The Effect of Some External Conditions upon Regeneration
and the Transformation of Organs
If we cut a piece ab, Fig. 59, from the stem 55 of Antennularia an-
tennina (Fig. 60), a hydroid, and put it into the water in a horizontal
position, new stems cd,
Fig. 59, may arise on its 4
upper side. The small
branches on the under '
side of the old stem ab v^
begin suddenly to grow
vertically downward.* In
appearance and function
these downward-growing
elements are entirely dif-
ferent from the branches
of the normal 'Antennu-
laria ; they are roots. FlG
In order to understand
better the transformation which thus occurs in these branches, it may
be stated that under normal conditions they have a limited growth
(see Fig. 60), are directed upward, and have polyps on their upper side
* Loeb, Untersuchungen ztcr physio I ogische Morphologie der Tkiere, II, 189 1.
2l8
DYNAMICS OF LIVING MATTER
ll
II
(Fig. 60). The parts which grow down (Fig. 59) have no polyps, but at-
tach themselves like true roots to solid bodies. Thus the changed posi-
tion of the stem alone, without any operation, suffices to
transform the lateral branches, whose growth is limited,
into roots with unlimited growth. The lateral branches
on the upper side of the stem do not undergo such a
transformation except in the immediate surroundings
of the place where a new stem arises. It seems that the
formation of a new stem also causes an excessive growth
of roots, possibly because the formation of new branches
causes the removal of substances which naturally inhibit
the formation of roots. If a piece from the stem be put
vertically into the water with top downward, the upper-
most point may continue to grow as a stem, while the
lowest point may give rise to roots. In this case, therefore,
a change in the orientation of organs has the effect of
changing the character of organs.
We have already mentioned the fact that in Eudendrium
the formation or regeneration of polyps is only possible in
the light.
In many hydroids, contact with solid bodies seems to
favor the formation of stolons, although such contact
is not the only
condition that
brings about this result. Fig-
ure 61 shows a piece of a stem
of Pennaria, a hydroid, which
was lying on the bottom of an
aquarium, and which formed
stolons at both ends. In Margelis, another hydroid, I observed
that, without any operation, the apical ends of the branches which were
in contact with solid bodies continued to grow as roots, while those
surrounded by sea water continued to grow as stems.
§3 IP
§
Fig. 60.
"^h^fk
Fig. 61.
7. The Role of Reversible Processes in Phenomena of
Regeneration
In all the cases mentioned thus far one point has not yet been dis-
cussed ; namely, where the material of which the new organs consist
comes from. In the case of plants, where the green leaves assimilate,
and the salts are taken up from the soil or water, this source is evident,
as it is also in the case of the animals which take up food; but in the
DYNAMICS OF REGENERATIVE PROCESSES
2T9
case of a piece from the body wall of an Actinian which has no digestive
organs, the material of the new tentacle can come only from one of two
sources, viz. from the chlorophyll (or parasitic algae?) which are con-
tained in the ectoderm, or through a hydrolysis of material contained in
the cells of the Actinian itself ; this latter case would be comparable to
Miescher's observation of the growth of the sexual glands at the expense
of muscular tissue. In the case of the polyp formation in Tubularia,
the transformation of the material of the stem into the polyp can be
directly observed (Bickford, Driesch, and others). It is even doubtful in
these cases whether a hydrolysis is necessary in any considerable amount,
and it looks as if the tissues could be utilized directly for the formation
of the polyp ; some hydrolysis may however occur. In the above-men-
tioned case of the transformation of a branch of Antennularia into a
root, the polyps that were on that branch first disappear. I cannot
make any definite statement as regards their fate, but it is not impossible
that the material of the polyps is used for the formation of the new roots.
I have observed more closely the transformation of an organ into
more undifferentiated material in Campanularia, Fig. 62, a hydroid.*
This organism shows
a remarkable stereo-
tropism. Its stolons
attach themselves to
solid bodies, and the
stems appear on the
side of the stolon
exactly opposite the
point or area of con-
tact with the solid
body. The stems
grow, moreover, ex-
actly at right angles
to the solid surface
element to which the
stolon is attached.
If such a stem be
cut and put into a
watch glass with sea
water, it can be observed that those polyps which do not fall off go
through a series of changes which make it appear as if the differ-
entiated material of the polyp were transformed into undifferentiated
material. The tentacles are first put together like the hairs of a
* Loeb, A?n.Jour. Physiology, Vol. 4, p. 60, 1900.
Fig. 62.
220
DYNAMICS OF LIVING MATTER
camel's-hair brush (Fig. 63), and gradually the whole fuses to a more
or less shapeless mass which flows back into the periderm, Fig. 64.
It follows from this that in this process certain solid constituents of the
polyp, e.g. the cell walls, must be liquefied. I pointed out the analogy of
these phenomena with Miescher's observations in the salmon. This un-
differentiated material formed from the polyp may afterward flow out
again, giving rise to a stem or a polyp ; to the former where it comes in
contact with a solid body, to the latter where it is surrounded by sea
Fig. 63.
water. This observation seems to indicate the possibility that the pro-
cesses of organization are reversible, in some cases at least.
Giard and Caullery have found that a regressive metamorphosis
occurs in Synascidians, and that the animals hibernate in this condition.
The muscles of the gills of these animals are decomposed in their indi-
vidual cells. The result is the formation of a parenchyma which con-
sists of single cells and of cell aggregates resembling a morula.*
Driesch found that when he isolated Clavellina that part of the ani-
mal containing the gills underwent a retrogressive transformation simi-
lar to that observed by Giard and Caullery, and that afterward these
masses gave rise to a new Ascidian.t The phenomena observed by
* I quote this after Driesch, Archiv fur Entwickelungsmechanik, Vol. 14, p. 247, 1902.
f Driesch, loc. cit.
DYNAMICS OF REGENERATIVE PROCESSES
221
Giard and Caullery, as well as the experiments of Driesch, resemble
those in Campanularia, and Driesch also expresses the opinion that
this is a case of reversibility of the processes of development.
The idea that the process of development is in certain forms reversi-
ble is also supported by the experiments of Frank Lillie on fresh- water
Planarians. Lillie found that adult fresh-
water Planarians if exposed to starvation
not only become gradually smaller in size
but ultimately return to an embryonic form !
These experiments have been repeated and
confirmed by Schultze.
There is a possibility that a definite kind
of chemical substances must be present in
order to make development, regeneration,
and growth possible. Such tissues as contain
these substances (or mixture of substances)
may be called embryonic. If this idea be
correct, and if it be true that phenomena of
development are reversible, — to a great
extent in a few forms, and to some extent
perhaps generally, — the question might be
raised whether or not one of the conditions
of regeneration is the transformation of adult
tissue into more embryonic tissue. If this
were true, the power of regeneration of an
organism might depend upon the degree
of reversibility of the processes of development in such a form. It is
certainly in harmony with such an idea that forms like Hydroids,
Ascidians, and fresh-water Planarians, where the reversibility of the
process of development is most outspoken, possess also the greatest
power of regeneration among animals. The idea suggested is further
supported by the fact that the power of regeneration by the embryo is
often considerably greater than the power of regeneration of the same
form in the adult stage. The tadpole of a frog is capable of regenerat-
ing a leg, while this is impossible in the adult frog.
This removes the contradictions into which we fall if we try to rep-
resent the power of regeneration as parallel to the position of an animal
in the natural system. We find Annelids, such as the leech, whose power
of regeneration is decidedly less than that of some vertebrates, e.g. the
salamander. If we cut off the tail of the salamander, a complete regen-
eration of this organ with all its parts, bones as well as spinal cord,
occurs. If we cut off a number of segments from a leech, the wound is
Fig. 64.
222 DYNAMICS OF LIVING MATTER
covered with epidermis and thus heals, but no regeneration of the lost
segment occurs. I have kept headless pieces of a leech alive for almost
a year, without any trace of a regeneration occurring. We thus see
that an Annelid may possess a much lower power of regeneration than a
vertebrate.
It has been maintained that the power of regeneration is due to
natural selection, and, therefore, runs parallel to the liability of an ani-
mal to injury. I do not believe that such ideas are of more value in
biology than they are in physics or chemistry. It is not very obvious
either why "nature" should care so much more to preserve the tail of
a salamander than the foot of the leech. Morgan has treated this sub-
ject exhaustively, and I refer the reader to his writings.*
* T. H. Morgan, Regeneration, New York, 1901 ; and Evolution and Adaptation,'Nevf
York, 1903.
LECTURE XII
CONCLUDLNG REMARKS
Biologists are confronted with two problems of transformation;
namely, the artificial transformation of dead into living matter, and the
artificial transformation of one species of plants or animals into another.
Will it be possible to solve these problems? It is certain that nobody
has thus far observed the transformation of dead into living matter, and
for this reason we cannot form a definite plan for the solution of this
problem of transformation. But we see that plants and animals dur-
ing their growth continually transform dead into living matter, and that
the chemical processes in living matter do not differ in principle from
those in dead matter. There is, therefore, no reason to predict that
abiogenesis is impossible, and I believe that it can only help science
if the younger investigators realize that experimental abiogenesis is the
goal of biology. On the other hand, our lectures show clearly that we
can only consider the problem of abiogenesis solved when the artificially
produced substance is capable of development, growth, and reproduc-
tion. It is not sufficient for this purpose to make proteins synthetically,
or to produce in gelatine or other colloidal material round granules
which have an external resemblance to living cells.
In this connection another problem may be mentioned; namely,
whether there exists a natural death or, in other words, whether death
is the necessary outcome of development, and whether rejuvenation and
the beginning of a new cycle of life are impossible. In man and higher
mammalians death seems to be caused directly or indirectly through
microorganisms or other injuries to vital organs. The example of cer-
tain plants, e.g. the Sequoia in California, shows that certain organisms
may five thousands of years.
I pointed out a few years ago that the egg is a valuable object for
the study of this problem. The process of fertilization of the egg is
a life-saving act. The mature egg which is not fertilized dies as a rule
very quickly under conditions under which the immature or the fertilized
egg remains alive. If, e.g., fertilized and unfertilized eggs of the same
female of Fundulus (a marine fish) are kept in the same vessel with sea
water or distilled water, the fertilized eggs remain all alive and develop,
while the unfertilized eggs die in a few hours and become putrid in a
223
224 DYNAMICS OF LIVING MATTER
day or two. The case of starfish eggs is possibly still more striking.
The egg of a starfish, Asterias Forbesii, is, as a rule, immature when
taken from the ovary, and maturates when put into sea water. Very
often not all the eggs of a female undergo maturation in sea water, and
I have found that maturation can be inhibited by putting the eggs into
slightly acid sea water. It was found that the eggs which maturate
but are not caused to develop die in a few hours, while the eggs that are
caused to develop or the eggs which fail to maturate (or are prevented
from so doing) will not die, even if kept in the same dish of sea-water.*
The eggs which are allowed to maturate, but are not caused to develop,
die just as well in perfectly sterilized sea water, in which the eggs keep
free from putrefaction for months, as in normal sea water or in sea water
to which cultures of bacteria of putrefaction have been added. These
and other facts indicate that in the mature egg processes occur which
lead invariably to the death of the egg under circumstances under which
the fertilized egg invariably keeps alive.
As far as the second problem of transformation is concerned, namely,
the transformation at desire of one species into another, conditions are
more favorable since De Vries has succeeded in actually observing the
transformation of one species into another.
De Vries discovered in experiments which have been carried on since
1886 in the most painstaking and laborious way, that from the seeds of
a certain plant, (Enothera Lamarckiana, there arise always a very
small number of plants which differ from the mother plants in definite
characteristics. f "These plants are from the very first true to seed!"
De Vries thus discovered that new forms arise from (Enothera La-
marckiana, not by gradual variation, as Darwin and Wallace had as-
sumed, but by a sudden jump. As an instance, the origin of the species
(Enothera gigas from (Enothera Lamarckiana may be mentioned. It
originated in De Vries's culture of 1895 in a single specimen, and this
first specimen was, as soon as it flowered, fertilized with its own pollen.
The action of insects was absolutely excluded. The following spring
the pure seed was sown (1897). The several hundred plants which
thus originated all differed in the same way from (Enothera Lamarcki-
ana, resembling the mother plant of (Enothera gigas. The species has
since remained constant. In the same sudden manner the other new
species of (Enothera originated from (Enothera Lamarckiana. To this
sudden, discontinuous form of evolution De Vries gave the term "muta-
tion." The observations of De Vries also explain the fact which Dar-
win's idea of gradual evolution failed to explain ; namely, that species
can and usually do remain constant for thousands of years. The plants
* Loeb, Pfliigers Archiv, Vol. 93, p. 59, 1902.
f Hugo de Vries, Die Mutationstheorie, Leipzig, 1901.
CONCLUDING REMARKS 225
found in Egyptian tombs do not differ from the species existing to-day.
According to De Vries, a period of constancy may be followed by an
explosive tendency to mutate, whereby new species arise suddenly, while
the original species continues to exist.
The most important fact, however, from our point of view is the per-
fect harmony between De Vries's theory of mutation and Mendel's ex-
periments on hybridization. The latter lead to the idea that hereditary
characteristics are transmitted by specific determinants in the sexual
cells, and that each characteristic must be represented by such a deter-
minant in the sexual cells. No two forms can have a closer resemblance
than corresponds to the difference between two determinants. If the
latter are comparable to the members of a series of compounds, e.g. of
alcohols, there is no more a transition possible between two species sepa-
rated by a difference in only one determinant than there is a transition
possible between the two neighboring alcohols of the same series. This
means that evolution must be discontinuous, as De Vries has actually
discovered it to be.
Not all the new species which originate from (Enothera Lamarckiana
are capable of existence. The first mutation De Vries observed was a
form having pollen unfit for fertilization. It goes without saying that
such a form cannot exist in nature. But other forms can exist, and do
propagate side by side with (Enothera Lamarckiana. The limitation
for newly produced species is not the struggle for existence, but a
faulty construction. The idea that mutation is working in a definite
direction is a mere anthropomorphism, and like all anthropomorphisms
is in contradiction with the facts.
INDEX
Abiogenesis, 223.
Acids, effect on heliotropism, 132.
Action currents, 69.
Alpheus, 215.
Amblystoma, galvanotropism in, 146.
skin secretion caused by constant
current, 103.
Amoeba, 57.
imitation of movements of, 56.
Amphipyra, stereotropism of, 157.
Amphoteric character of proteins, 35.
Anaesthetics, 6.
Antagonistic effects of salts, 46.
of K and Ca salts, 86.
of Na and Ca or Mg salts, 79.
of salts with univalent cations and
bivalent or trivalent cations, 47.
Antennularia, geotropism of, 148.
regeneration in, 217.
Aphides, 4, 165, 187.
Araki, 18.
Arbacia egg, absence of complicated
structure, 193.
artificial parthenogenesis in, 167.
development of deformed egg, 193.
effect of NaHCC>3 on development
of, 97.
limit of divisibility of, 167.
Arrhenius, 108, 113.
D'Arsonval, 55, 58.
Artificial hybridization, 162.
Artificial parthenogenesis, 165.
Aspergillus, 72.
Assimilation in plants, effects of light of
certain wave lengths, 115.
Associative memory. 6.
Asterias, speedy death of unfertilized
maturated eggs, 224.
sperm of, used to fertilize eggs of
sea urchin, 162.
Asterina, artificial parthenogenesis, 172.
sperm used to fertilize sea-urchin
egg, 162.
Astrospheres, orientation of, 65.
Autoxidizable substances, 13.
Von Baer, 161.
Bancroft, 103, 141.
Bardeen, 210, 213.
Barium salts, effects of, on peristalsis, 93.
on Poly orchis, 93.
on rhythmical contraction of muscle,
87.
on secretion, 93.
Barrat, 101.
Bataillon, 175.
Bateson, 186.
Van Bemmelen, 43.
Bernard, 21.
Bernstein, 55, 57, 69.
Berthold, 57.
Berzelius, 7.
Bicarbonates, r61e of, in preservation of
life, 96, 97.
Bickford, Miss, 204.
Von Biebra, 41.
Blasius, 145.
Blastomeres, differentiation of, 196.
isolated, development of, 30.
Blue rays most effective in heliotropism,
127.
Bock, 94.
Bordet, 23, 154, 182.
Born, 162, 190.
Boveri, 30, 60, 164, 181, 194.
Brachystola, 188.
Bredig, 27, 37.
Brenner, 145.
Broca, 19.
Briinings, 69.
De Bruyn, 26.
Buchner, 21.
Budgett, 21, 104, 143.
Bugarsky, 96.
Buller, 153.
Bullot, 51, 175.
Bunge, 23.
Butschli, 32.
Butterflies, 139.
larvae of, 126.
Calcium precipitants, 80.
in phenomenon of contact reaction, 83.
Calcium salts, in muscular contraction, 79.
in coagulation of milk, 89.
Campanularia, transformation of organs
in, 219.
Carbonates in blood, 96.
227
228
INDEX
Carbon dioxide, as plant food, 62.
effect of temperature on production
of, 108.
production in active nerve, 68.
in cell division, 62.
in lack, of oxygen, in seeds, 22.
in muscles in absence of oxygen, 23.
through enzyme action, 21.
Carroll, 27.
Castle, 164, 186.
Catalase, 27.
Catalytic action, 8.
of lipase, 9.
of platinum-black, 11.
inhibited by poisons, 27.
in respiration, 13.
Catelectrotonus imitated through action
of calcium precipitants, 102.
Caullery, 220.
Cell division, chemical processes in, 61.
chromosomes in, 60.
effect of temperature on, 59.
oxygen in, 16.
physical phenomena of, 62.
dependence on of size of cell, 59.
Centrosome, 64.
Cerianthus, 207, 209.
Chabry, 197.
Chtztopterus, artificial parthenogenesis
produced by K-salts, 166, 174.
Chemotropism, 152.
biological significance of, 155.
reaction of bacteria and Infusoria to
oxygen, 153.
reaction of antherozoa of ferns to
malic acid, 153.
Chevreul, 107.
Child, 209, 213.
Chilomonas, chemotropism of, 154.
Chlorophyl, 115.
Christen, 107.
Chromosomes, 60, 61, 176.
Chun, 195.
Ciona, 209.
Cladocera, 187.
Clark, 149.
Clausen, 108.
Clavellina, 220.
Cleavage plane, centrosomes in relation
to, 64.
Hertwig's law, 64.
Cohen, no.
Cohnheim, 23.
Colloidal character of living matter, 1.
Colloidal solutions, 34.
electrical charge of, 34.
precipitation by salts, 36.
relation to cell life, 37.
amphoteric colloids, 35.
Colloids, nature of, 1, 33.
dissociated, 99.
Compensatory hypertrophia, 201.
Compensatory motions, 149.
Conklin, 196.
Consciousness, 6.
Constant current, 99.
stimulation at cathode on making,
99, 102.
stimulation at cathode in Infusorians,
. J.°3-
disintegration by, 103.
Contact irritability, produced by sub-
stances which precipitate calcium, 83.
effect of K-salts on, 84.
Copepods, heliotropism of, 129.
phosphorescence of, 67.
Correlation in regeneration, 213.
Correns, 183.
Cottrell, 95.
Crampton, 191, 196.
Cramer, 107.
Cremer, 12, 25, 176.
Ctenolabrus egg, effect of lack of oxygen,
17, 19.
Ctenolabrus, heart of embryo, 19.
Ctenophores, structure in egg of, 195.
Cucumaria, geotropism of, 149.
Cuenot, 186.
Cushny, 93.
Von Cyon, 217.
Cytotropism, 159.
Czapek, 148.
Darwin, 119, 225.
Death, natural, 4, 223.
Delage, 151, 152, 164, 173, 179, 186.
Dentaliiim, 197.
Determinants, in heredity, 3, 184.
in the sexual cells, 225.
Development, rate affected by tempera-
ture, no.
Dewitz, 153, 156, 166.
Dinophilns, 187.
Disoxidizable substances, 13.
Distilled water, toxicity of, 46, 51.
Divisibility of living matter, 29.
Dominant characteristics, 184.
Driesch, 30, 59, 61, 64, 115, 158, 181, 192,
194, 220.
Duclaux, 11, 16, 106, 113.
Duhamel, 200.
Van Duyne, 211.
Dzierzon, 165.
Earthworm, regeneration in, 214.
Egg structure, 2, 31, 191, 194, 195-
simple character of, 193, 195.
Ehrlich, 23.
Electrical phenomena, in muscle and
nerve, 68.
in plants, 69.
general occurrence in connection with
life processes, 70.
Electrical stimulation, 98.
by constant current, 99.
by induction, 99.
INDEX
229
Electrical stimulation {continued)
in Infusoria at cathode of constant
current, 103.
Electrolytes in liquids of the body, 68.
role of in living matter, 71-106.
rhythmical contractions only in, 78.
Elvove, 19.
Embryos, from deformed eggs, 193.
from 'fused eggs, 194.
from isolated blastomeres, 192.
Emulsion structure of protoplasm, 31.
Engelmann, 17, 54, 153.
Engler, 14.
Enzymes, stereochemical theories of, 24.
theory of intermediary reactions, 26.
reversible action of, 9.
Eudendrium, effect of light in organ for-
mation, 115.
heliotropism of, 120.
Ewald, 215.
Eyes, compensatory motions of, 149.
Faraday, 66.
Farkas, 95.
Fermentation, alcoholic, 21.
Fertilization, 161.
membrane, 162.
produced in unfertilized eggs by fatty
acids, 168.
produced by hydrocarbons, 169.
formation of, antagonized by H-ion,
170.
Fischel, 195.
Fischer, Alfred, 37, 65.
Fischer, Emil, 24.
Fischer, M. H., 94.
Foam structure, 31.
Forteg, 114.
Fraenckel, 95.
Freundlich, 35, 36.
Friedenthal, 95, 182.
Fundulus egg and embryo, effect of lack
of oxygen, 17.
effect of salts, 46, 50.
effect of distilled water, 45.
Fungi, nutritive solutions for, 71.
Galvani, 68.
Galvanotropism, 140.
in Amblystoma, 146.
in Palcrmonetes, 144.
in Paramcecium, 142.
in Polyorchis, 141.
in seedling plants, 145.
Gammarus, 46, 50, 51, 74, 77, 97, 128.
Ganglion cells, effect of lack of oxygen, 18.
Garrey, 154.
Gaule, 97.
Gels, 1, 37.
Geotropism, 147.
in Antennularia, 148.
in Cucumaria, 149.
in crustaceans, 149.
Geotropism {continued)
in plants, 147.
possible connection with internal
ear, 151.
Geppert, 21, 27.
Gerassimow, 59.
Giant embryos, 194.
Giard, 220.
Gies, 175.
Giescbrccht, 67.
Glycogen, 12.
Godlewski, 17, 22, 204.
Goltz, 6, 150, 158, 215.
Gonionemus, 81, 91.
Gordon, 50.
Gotschlich, 147.
Graham, 1.
Greeley, 112.
Growth, need of oxygen in, 17.
Gruenbaum, 182.
Guyer, 186.
Hamburger, 44.
Hardest)', 21.
Hardy, 31, 32, t,Z, 35, 43-
Harless, 41.
Heart of Ctenolabrus embryo, 20.
Heartbeat, conditions in normal, 91.
reaction velocity in, 109.
Heat, effects of, 106.
biological effects, 111.
chemical effect, 106.
coagulation of proteins, 107.
coagulation of colloids a function of
time, 108.
effect on coefficient of partition, in.
poisons, activity of, influenced by,
in.
Heliotropic reactions, sense of, 130.
reaction velocity in, 130.
effect of differences of intensity of
light, 131.
sense of heliotropism reversed by
chemical substances, 131.
changes in intensity of heliotropism by
chemical substances, 132.
intensity of reaction at certain stages
in life history, 133.
sense of reaction changed in certain
stages of development, 133.
in larvje of Limulus, 133.
effect of temperature on sense of reac-
tion in Polygordius, and in Coppods,
effect of light on sense of reaction in
nauplii of Balanus, 134.
Heliotropism, of sessile organisms, 117.
green, blue, and violet end of spec-
trum most effective, 117.
theory of heliotropic bending, 118.
in Eudendrium, 120.
in Spirographis, 122.
in SerpuJa, 123.
230
INDEX
Heliotropism {continued')
of free-moving organisms, 124.
in larvae of Eudendrium, 125.
in Aphides, 126.
in caterpillars of Porthesia, 126.
direction of motion determined
by direction of light rays and not
by intensity, 126.
negative heliotropism in animals,
128.
Helmholtz, 53.
Hemiptera, spermatozoa of two kinds in,
188.
Hemolysis, 182.
Henking, 188.
Herbst, 75, 158, 169, 213.
Hereditary effects of the spermatozoon
and the egg, 179.
Heredity, prevailing influence of the egg
in early stages of development, 179.
influence of egg and spermatozoon
in adult, 180.
influence of the nucleus in, 180.
Mendel's experiments, 180, 183.
chemical compounds in, 180.
determination of sex, 186.
egg structure in heredity, 191.
Hermann, 22, 58, 70, 145.
Hertwig, O., no, 179.
Her twig, O. and R., 64, 65, 164, 166, 169.
Hertwig, R., 63, 166.
Hertzian waves, 112.
Herzog, 13.
Heteromorphosis, 201 ff.
in Ciona, 209.
in Planarians, 210.
Hildebrandt, 124.
Hill, 9, 11, 12.
Hippiscus, 188.
Hober, 44, 50, 95.
Van't Hoff, 108.
Hoffmann, 94.
Holmes, 134, 139, 158.
Hoppe-Seyler, 16, 114.
Hybridization, 3, 161 ff.
in vertebrates, 161.
Mendel's experiments, 183.
heterogeneous, in Echinoderms, 162.
Hydatina, 190.
Hypertonic solutions, nuclear division in,
. 63- .
in artificial parthenogenesis, 170.
Hypophysis, 216.
Imbert, 55, 57.
Instinctive reactions, 158.
Instincts, 5, 186, 189.
Ion-colloids, 82, 95.
Ion-proteids, 78, 167.
Irritability, theory of, 78.
Jacquet, 14, 15.
Janssens, 164.
Jennings, 155.
Jones, 27.
Jorissen, 114.
Kastle, 9, 10, 11, 14, 19, 26, 28.
Kellogg, 133, 190.
Kirchoff, 8.
Knight, 147. _
Knop's solution, 71.
Kofoid, 196.
Kolliker, 66.
Korschelt, 187.
Kostanecki, 175.
Krafft, 34.
Kreidl, 151, 152.
Kiihne, 103.
Kulagin, 166.
Kuliabko, 18.
Kutscher, 12.
Laminaria, 206.
Landois, 182.
Lanice, 196.
La Place, 7.
Lavoisier, 7.
Lefevre, 174.
Lenhossek, 187.
Lens, regeneration of, 215.
Leuckart, 165.
Leuwenhock, 161.
Lewis, 215.
Liebermann, 96.
Liebig, 24.
Von Liebig, G., 22.
Light, photochemical effects, 113.
effect on assimilation in green plants,
114.
waves effective in assimilation, 115.
heliotropic effects, 117.
waves most effective in heliotropism,
"7-
reactions of animals to changes of
intensity, 135.
Lillie, Frank, 175.
Lillie, Ralph, 16, 65.
Limulus larvae, negative heliotropism in,
128.
reversal of heliotropism, 133.
Linder, 51.
Lingle, 8i,_ 83.
Lipase action, reversible, 9.
imitated by platinum-black, n.
Liquefactions in absence of oxygen,
20.
Living matter, limit of divisibility, 29.
foam structure and emulsions, 31.
colloidal character of, 33.
Locke, 51, 76.
Loevenhart, 9, 10, n, 14, 26, 28, 88.
Loew, 26.
Ludloff, 142.
Lymnceus, 196.
Lyon, 62, 150, 152, 159.
INDEX
231
MacCallum, 44, 93.
Mach, 145, 151.
Maltase, 11.
Margelis, 218.
Massart, 154.
Mathews, 92, 173.
Maupas, 190.
Maxwell, 103, 144, 157.
Mayer, 53.
McClung, 188, 190.
Mead, 166.
Medusa, analogy of contractions to heart-
beat, Si.
Membrane, fertilization, 162.
Membranes of precipitation, 38.
Mendel, 3, 180, 183, 1S4, 186.
Von Mering, 23.
Merogony, 164, 179.
Metabolism, different in presence and in
lack of oxygen, 18.
Metal proteids, 78.
Meyer, 6, 40, 216.
Miescher, 4.
Minkowski, 23.
Mollusks, artificial parthenogenesis in, 175.
Morgan, 59, 63, 159, 164, 166, 192, 194,
206, 210, 213, 214, 222.
Mortality of hybrids, 183.
Miiller-Hettlingen, 145.
Muscle, electrical phenomena in, 68.
CO2 produced in, 68.
tone affected by K and Ca, 86.
Muscular contraction, 52.
hypotheses of, 53.
Engelmann's hypothesis, 54.
Bernstein's hypothesis, 57.
Imbert's hypothesis, 57.
Mutation theory, De Vries', 3, 224.
Narcotics, 40.
Negative wave, 169.
Neilson, n.
Nereis, stereotropism of, 157.
Nernst, 40, 100.
Nerve, CO2, produced in, 68.
electrical phenomena, 68.
impulse, 70.
Nervous disease, possible chemical cause
of, 92.
Nervous system, influence on regenera-
tion, 213, 216.
may convey chemical substances, 216.
Norman, 63, 166.
Nuclear membrane, 65.
Nucleus, in cell division, 60.
division of, without division of pro-
toplasm, 63.
in heredity, 180.
Nussbaum, 16, 29, 165, 190.
Nutritive solutions for green plants, 71.
for fungi, 72.
for animals, 74.
Nuttall, 182.
Ocneria, 190.
CEnolhera, 224.
Oker-Elom, 69.
Oligodynamic effects, 73.
Ophelia, artificial parthenogenesis in, 175.
Organisms as chemical machines, 1.
Orthoptera, spermatozoa of, 188.
Osmotic pressure and exchange of liquids
between the cells and surrounding
liquids, 41.
effect on cell division, 63.
Osterhout, 207.
Ostwald, Wilbelm, 8, 9, 69.
Ostwald, Wo., 51, 97, 149.
Otolith organs, 151.
Oudemans, 190.
Overton, 6, 40.
Oxidases, 13.
Oxidation, in living matter, 7, 13 ff.
through peroxides, 14.
in mature egg, 177.
Oxygen, in cell division, 16.
in fermentation, 16.
in segmenting eggs, 17.
in growth and regeneration, 17.
in Infusorians, 21.
in phosphorescence, 67.
in rhythmical contraction of heart
muscle, 82.
as a protective substance, 18.
irreversible changes in lack of, 18.
bacterial poisons more virulent in
absence of, 19.
structural changes in lack of, 19.
effect of certain poisons resembles
effect of lack of oxygen, 21.
Palczmon, otoliths in, 151.
Palccmonetes, galvanotropism in, 144.
ParamcEcium, galvanotropism in, 142.
Parker, 139.
Parthenogenesis, natural, in Aphides, 165.
in bees, 165.
in starfish, 173.
artificial, by raising concentration of
sea water, 167.
in Chatopterus by addition of a
K-salt, 174.
in asterias, 173.
in Strongylocentrotus, 167 ff.
in Thalassemia, 174.
in Ophelia, 175.
in mollusks, 175.
in vertebrates, 175.
Pasteur, 17, 19, 21, 24.
Pauli, 32, 78, 108.
Pemsel, 96.
Pennaria, 218.
Permeability of plant cells, 41.
of muscle, 42.
Peroxides in oxidation processes, 14.
Petromyzon, 175.
Petrunkewitsch, 165.
232
INDEX
Pfcffer, 153.
Pfiiiger, 66.
Phosphorescence, 66.
Photochemical reactions, in assimilation in
plants, 114.
in heliotropism, 119.
Pictet, in.
Picton, 51.
Fieri, 175.
Pigment granules in Tubularia, 205.
Planarians, reactions to light, 136.
heteromorphosis and regeneration in,
210.
Planorbis, 196.
Plants, nutritive solutions for, 71.
Platinum-black, enzyme action of, 11.
Polarity in Tubularia, due to a current, 203.
Polygordius, heliotropism in, 133.
Polyorchis, effect of ions on, 87, 88, 91.
galvanotropism in, 141.
Polzeniusz, 22.
Porthesia, heliotropism of, 126.
Potassium, non-dissociable compounds
with protoplasm, 73.
Prentiss, 152,
Protective solutions, 77.
Proteins, amphoteric character, 35.
Proteolytic enzymes, general occurrence
of, 12.
Protoplasm, structure of, 31.
Protoplasmic motion, 55.
Przibram, 215.
Psychologv of lower forms, 158.
Purgative effects of salts, inhibited by
Ca, 93.
produced by Ca precipitants, 93.
Purkinje, 145.
Pycnopodia, 162.
Pyrrhocoris, spermatozoa of, 188.
Quincke, 32, 38, 40, 55.
Radiant energy, origin of in organisms, 66.
general effects on living matter, 112.
Radiation pressure, 113.
Radl, 113, 150.
Radziszewski, 67.
Ramsden, 38.
Raulin, 72, 79.
Rayleigh, 32.
Reaction of living matter, 95.
of sea water, 95.
effect of green plants on, 98.
Reaction velocity, effect of heat on, 108.
in biological processes, 109.
in heartbeat, 109.
in heliotropism, 130.
Recessive characteristics, 1.84.
Regeneration, in plants, 200, 207.
in Cerianthus, 207.
in Planarians, 210.
in earthworm, 214.
influence of central nervous system, 213.
Regeneration {continued)
correlation in, 213.
effect of external conditions 01;, 217.
distribution in animal kingdom, 221.
and natural selection, 222.
Regenerative processes, 199.
Reid, 34.
Respiration as a catalytic process, 13.
Reversible processes, in enzyme action, 9.
in regeneration, 218.
in Campanularia, 219.
in Planarians, 221.
Rheotropism, 159.
Rhythmical contractions, of skeletal mus-
cle, 78.
effects of salts of univalent metals, 78.
effects of Ca and Mg, 79.
absence in non-electrolytes, 82.
effect of Ba salts, 87.
Richardson, 114.
Richet, 19.
Ringer, 87.
Ringer's solution, 75.
Rogers, 75, 97.
Romanes, 80.
Rotifers, 187.
Roux, 64, 66, 159.
Rusch, 76.
Sachs, 59, 121, 199, 200, 201.
Salmon, 4, 198.
Salts, antagonistic effects of, 46, 75 ff.
diffusion into cells, 42.
Schmiedeberg, 17, 93.
Schoenbein, 21, 24, 27, 114.
Schultze, 197.
Schweitzer, 145.
Secretion, 44, 50.
produced by galvanic current, 93.
produced by Ca precipitants, 93.
formation of egg membrane resembles
secretion, 174, 177.
Segmentation, need of oxygen in, 17.
Selective power of cells, 72.
Semicircular canals, 150.
Semipermeable membranes, 39, 69, 101.
Sensory nerves, irritability increased by
Ca precipitants, 91.
Sequoia, 5, 223.
Serpula, 123.
Setchell, 106, in.
Sex, determination of, 186.
in egg, 187. __ ,
in spermatozoon, 188.
attempts to influence, 190.
Sexual characters, secondary, 190.
Siebold, 165.
Snyder, 109.
Sodium, unimportant for plants, 72.
importance in muscular contractions,
79-
Sols, 1.
Spallanzani, 161.
INDEX
233
Species, transformation of, 224.
Speck, 6.
Spemann, 215.
Spermatozoa, stereotropism of, 156.
specific nature of, 162, 163.
effect of alkali on, 163.
nature of action, 176, 178.
Spiro, 96.
Spirographis, 122.
Spitzer, 15.
Starling, 34.
Starvation, effect on Planarians, 221.
Stereochemistry and enzyme action, 24.
Stereotropism, 155 ff.
in spermatozoa of Periplanata, 156.
in Tubularia, 156.
in Amphipyra, 157.
in worms, 157.
Stevens, Miss, 206.
Stimulation, 98, 105, 180.
Stoklasa, 22.
Strassburger, 130.
Streaming phenomena, 65, 204.
Strongylocentrotus eggs, fertilization imi-
tated artificially, 2, 167 ff.
structure of, 31.
effect of electrolytes on development
of, 75- , ,
effect of NaHCOs on development
of, 75, 97-
fertilized with starfish sperm, 162.
Surface films, 32, 38.
Surface tension, 55.
in protoplasmic motion, 55.
in muscular contraction, 57.
in fertilization process, 163.
Taylor, 9, 10.
Temperature, upper limit of life, 106.
coagulation of proteids, 107.
effect on reaction velocity, 108.
effect on CO2 production, 108.
effect on rate of heartbeat, 109.
effect on development of frog's
eggs, 1 10.
lower limit of life, no.
other biological effects, 112.
effect on heliotropism, 131.
Tetanus toxin, 216.
Thalassemia, 174.
Thenard, 8.
Thigmotropism, 155.
Thyroid gland, 216.
Tichomiroff, 165.
Towle, Miss, 134.
Transfusion of blood, 182.
Traube, 13, 24, 33, 38, 45.
Traube's artificial membranes, 39.
Tropceolum, 199.
Tropisms, 5.
theory of, 138.
Tschagovetz, 69.
Tschermak, 183.
Tuhularia, necessity of oxygen in regen-
eration, 17.
influence of bicarbonates on, 96.
stereotropism of, 156.
regeneration in, 202.
polarity in, 202.
heteromorphosis, 203.
Turgidity in tentacles of Cerianthus, 208.
Twins, 186.
Verworn, 142.
Vogel, 113, 114-
Volta, 68.
De Vries, 3, 183, 186, 224, 225.
Waller, 68, 70.
Warburg, 101.
Whitman, 197.
Wild, 14.
Willow twig, regeneration in, 207.
Wilson, 32, 178, 189, 192, 196, 216.
Winkler, 175.
Winter eggs, 187.
Woehler, 7.
Wortmann, 119.
Yeast, 12.
Young, 21.
Von Zeynek, 10 1.
Zinc, in nutrient solution for Aspergil-
lus, 73.
Zoethout, 84, 86.
Zur Strassen, 194.
Zymase, 21.
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Contents. — I General Introduction II. The External Factors of Regeneration in Animals. III. The
Internal Factors of Regeneration in Animals. IV. Regeneration in Plants. V. Regeneration and Liability to
Injury. VI. Regeneration of Internal Organs. Hypertrophy. Atrophy. VII. Physiological Regenera-
tion. VIII. Self-division and Regeneration. Budding and Regeneration. Autotomy. Theories of Autotomy.
IX. Grafting and Regeneration X. The Origin of New Cells and Tissues. XI. Regeneration in Egg and
Embryo. XII. Theories of Development. XIII. Theories of Regeneration. XIV. General Considerations
and Conclusions.
" The high character of the Columbia University Piiological Series is more than maintained by its latest
publication — Professor Morgan's book on ' Regeneration.' It is rare indeed to find a book which contains so
large an amount of research work and which is at the same time of such general interest and importance. This
is no mere discription of the peculiar and bizarre ' dime museum experiments' of experimental zoology, but
rather a thorough treatise on some of the more important methods and results of the new morphology.
" In this work the author has been one of the most productive and at the same time one of the most careful
investigators. He saw, as apparently few others did, that the development of fragments of eggs and embryos
was at bottom the same problem as the regeneration of parts of adult organisms, and during the past ten
years he and bis pupils have done a surprising amount of work on the regeneration of embryos and adults.
There is probably no other living man so well fitted to treat this subject." — Science, April, 1902.
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Vol. I. From the Greeks to Darwin. OSBORN
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Vol. VII. Regeneration. MORGAN
Vol. VIII. Dynamics of Living Hatter. LOBB
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Vol. IX. Structure and Habits of Ants. Professor W. M. WHEELER, of the American
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Accession no.
AuthorLoeb, J.:
The dynamics of
living matter .
1906.
Call no.i . . i .
OP509 ^<J
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